RIP

Liam Payne had multiple substances in his system when he died in Argentina, including a mix of drugs known as "pink cocaine" ... according to the initial results from his autopsy.

Law enforcement sources in Buenos Aires tell TMZ ... the toxicology results for the late One Direction singer are in, and they show he had cocaine and crack in his body when he fell to his death from a third-floor balcony at a Buenos Aires, Argentina hotel.

Forensic examiners, we're told, also found "Cristal" in his blood, which is the Argentinian version of methamphetamine. ABC News first reported the news, adding that ketamine, ecstasy and "pink cocaine" were also part of the drug cocktail in his system.

Justin Bieber is thinking of Liam Payne and his fans in the days following the One Direction alum's death ... encouraging those who love the singer to grieve as they see fit.

The pop star posted on his Instagram Stories Monday, where he addressed Liam's passing by sharing a fan video featuring the many vigils assembled in LP's honor.

A caption on the clip read ... "Rest Easy Liam."

Cops in Argentina are digging deep to get answers in Liam Payne's death, and TMZ has learned they're questioning all the employees at the hotel where he fatally fell from his third-story balcony.

Law enforcement sources in Buenos Aires tell TMZ ... cops are focusing on one hotel employee in particular who they suspect might have supplied the late singer with anti-anxiety meds reportedly found in Liam's room at the CasaSur Palermo Hotel.

We’re told police are investigating to determine whether the employee supplied Liam with any of the drugs found in his system -- including cocaine, crack, ketamine, ecstasy and a form of crystal meth called "cristal" -- according to initial autopsy results.

Liam Payne's fans are pouring their grief into his music, with streaming numbers for both his solo tracks and One Direction songs surging on Spotify.

Before his tragic death last week, Liam had 4.7 million monthly listeners on the streaming app, but that number has nearly doubled to 8 million now. Plus, his 2019 debut single "Strip That Down" featuring Quavo has racked up over 800,000 additional streams since then.

The numbers are also booming for One Direction -- they had 42.4 million monthly listeners before, and now they're nearing 50 million.

AJ McLean is remembering Liam Payne as "a light" in his life following the singer's recent death ... looking back on their time together working on a new Netflix show.

The Backstreet Boys member addressed the late One Direction star's passing at LAX, where he shared how he and Liam became friends while working on "Building the Band," a music competition series where singers get a chance to build the next great pop group.

AJ says they just finished wrapping the TV show ... where he, Liam, Nicole Scherzinger and Kelly Rowland worked closely together over a 6-week period and had "a great time."

Tragedy struck the Houston area when a helicopter collided with a radio tower last night and crashed to the ground ... killing 4 people, including a child.

The moment the chopper hit the radio tower was caught on camera ... and one witness captured the fiery aftermath of the tragedy.

Watch the vid ... a fireball plummets to the ground as debris begins to crumble around it -- shocking residents in the area. Smoke fills the air, as the surrounding area is set ablaze.

Liam Payne's ex-GF, Danielle Peazer, has revealed the last message he sent her just weeks before his tragic death.

Danielle shared a heartfelt IG tribute to her ex Sunday, looking back at their time together and emphasizing that all was good between them since their 2013 breakup -- in fact, Liam had recently sent her a sweet message, saying he was super happy for her and her new family.

Referencing her partner Sonny Jay and their daughter Mia, Danielle wrote directly to Liam ... "Receiving a message from you a couple of weeks ago expressing your happiness for the love I found with Sonny and Mia is something I'll cherish forever."

Liam Payne's girlfriend Kate Cassidy is stepping back into the public eye after the tragic death of her pop star boyfriend.

The late singer's love has been spotted for the first time since the One Direction alum fell to his death in Buenos Aires, Argentina last week ... and the influencer appears to be keeping a low profile in the wake of the tragedy.

Kate, who had been dating Liam for about 2 years before his death, was seen out and about in Florida Sunday, where she ran an errand to grab some dog food not far from her Palm Beach abode.

Liam Payne's sister Nicola is hoping the singer has "finally found peace" after he fell to his death in Argentina last week.

The One Direction alum's older sister posted on Instagram in the aftermath of Liam's death ... paying tribute to the late pop star and revealing her initial reaction to the tragic news.

As Nicola put it ... she learned of Liam's passing through a news notification on her phone, which left her hoping the update was "untrue."

She added ... "I have spent days hoping that it was a mistake and somebody got it wrong. You were truly too good for this earth, you are an angel who just lived for making people smile and happy. You have always shown kindness to everyone you met and it shows with just how many people have confirmed what we always knew!"

As Nicola continued, she declared herself and the rest of the Payne family Liam's "biggest fans always and forever" ... praising her little brother for his "brilliant" talent and dedication.

Before signing off her note, Nicola promised to keep Liam's legacy alive, especially for the singer's son, Bear ... who he welcomed with Cheryl Cole in 2017.

She noted ... "We will make sure Bear knows about his daddy and how much you loved him, we promise this."

Nicola's tribute comes shortly after Liam's other big sister, Ruth Gibbins, posted to social media, in which she apologized for not being able to "save" the singer.

Countless others have honored Liam in the wake of his passing, too ... including Harry Styles, Zayn Malik, Louis Tomlinson, Niall Horan, Simon Cowell, Ed Sheeran and Rita Ora.

As TMZ previously reported, Liam fell to his death from a third-floor balcony at the CasaSur Palermo Hotel in Buenos Aires last Wednesday. The singer had been in Argentina to support his former 1D bandmate Niall's concert at the Movistar Arena earlier in the month ... ultimately choosing to extend his visit.

Police have said Liam jumped from his hotel balcony ... and that a possibly hallucinogenic drug, called "cristal," may be to blame. However, police are waiting for final test results for substances found in Liam's hotel room before confirming. The investigation is ongoing.

Madonna attended a packed show at Madison Square Garden this week ... no, it wasn't her own -- it was Billie Eilish's instead!

The legendary pop star stopped by the legendary New York City venue with her boyfriend Akeem Morris to watch Billie and her brother Finneas put on their show.

No special VIP tickets for the Queen of Pop BTW ... looks like she's in the crowd like everyone else -- jamming out and chattin' in her man's ear.

Zayn Malik's still reeling from Liam Payne's death ... announcing moments ago he's postponing his "Stairway to the Sky" tour after the "heartbreaking loss" this week.

The singer-songwriter posted a short message to his Instagram story ... telling fans he needs to push off the U.S. leg of his tour -- and, he's rescheduling for January.

ZM says he plans to post the updated dates in the coming days ... and, he's thanking fans for their compassion and understanding during this time.

Liam Payne stayed in one other hotel before checking into the one where he died, and did party pretty hard while there -- but, despite reports, it wasn't enough to get him kicked out of the fancy spot.

Liam and his girlfriend Kate Cassidy were staying at the Palacio Duhau Park Hyatt in Buenos Aires during the week prior to his death, and a staffer there tells TMZ ... the couple was definitely in celebratory vacay mode.

We're told Liam did get "pretty drunk" on some nights, but he was never belligerent. In fact, he was, at least, trying to be entertaining ... as he would sometimes sing in the lobby.

Shawn Mendes was so overcome with emotion over the death of Liam Payne ... the singer paused his NYC concert Friday night to pay tribute to his pal.

Shawn was performing at the Brooklyn Paramount Theatre when he took a moment to tell the crowd that the One Direction star was a "beautiful soul" ... and the shocking news of his death was "devastating."

SM emotionally lamented ... “Liam, we love you. The world is crying for you, brother. And we’re all praying for your son and your family, and I miss you, man. So this one’s for you tonight, Liam, from all of us.”

Liam Payne's sister has broken her silence after the tragic death of the One Direction star ... and her message is absolutely devastating.

Ruth Gibbins posted a lengthy statement to her Instagram page along with several sweet photos of the siblings -- all to express how much she loved her brother and her unbearable pain, which included, "I'm sorry I couldn't save you."

She began with, "I don't believe this is happening. Many times have I poured my heart out publicly with pride about Liam but never much about life as his sister ... Liam is my best friend."

7:40 PM PT -- Although police say Liam's behavior sounds consistent with that of "cristal" users, they still don't know if that drug was present in the room. We're told they're still waiting for test results on the narcotics and medications they recovered.

Liam Payne was potentially under the influence of a potent drug, known to cause psychotic attacks and hallucinations, when he died ... according to police in Argentina.

Cops in Buenos Aires tell TMZ ... their operating theory is Liam was high on a substance called "cristal," which police say causes users to experience extreme highs and extreme lows, often making them aggressive.

Photos from inside Liam's hotel room show the place trashed ... his TV was smashed and there was drug paraphernalia in the room, which was littered with broken objects.

Liam Payne's father is sharing his grief with his son's fans in Argentina ... standing with them in an incredibly poignant moment right outside the hotel where Liam died.

The heartbreaking scene played out Friday evening in Buenos Aires ... Geoff Payne solemnly walked around the makeshift memorial fans have created on the sidewalk in front of the CasaSur Palermo hotel.

As Liam's dad looked at all the flowers, letters and candles ... fans observed a moment of silence in honor of the singer.