Dancing with the Stars

We're told the threats began to come in last week, after Bristol and Mark made the finals. Execs on the show told Mark to stop tweeting because it was inciting people. Mark complied.

Sources connected with the show tell us extra security will be on hand tonight for the show. And, if Bristol and Mark head to New York, execs are talking about breaking format and not doing their interview outside in Times Square -- but rather in the studio, where it's more secure.

TMZ broke the story ... a staffer on the show opened a "fan letter" to Bristol on Friday and white powder fell out. Turns out it was talcum powder, but the FBI is investigating nonetheless.

The rep continues, "Initial field screening was negative for hazardous substances but will be transported to a regional lab for further testing. A joint investigation is continuing."
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Cops and other emergency responders raced to CBS Television City studio late Friday after a white powder substance was discovered by a member of the "Dancing with the Stars" staff ... and sources tell us Bristol Palin may have been the intended target.

Law enforcement sources tell us a powder substance was discovered by a member of the "Dancing" staff ... and sources connected to the show tell us a section of the studio containing "Dancing" offices was evacuated.

Local authorities claim Steven Cowan (left) told officers that he felt Palin was not a good dancer and that she was only on the show because of her famous mother.

Officials say Cowan was so pissed after Monday's show -- that he fired at his television set and then aimed the gun at his wife ... though she managed to escape the house.

The SWAT team surrounded the home -- but negotiators were able to talk Cowan into surrendering early Tuesday morning. Authorities claim Cowan suffers from bipolar disorder.

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The Sitch's manager (pictured above) tells us the car was only a rental -- and it was the manager's rental, not The Situation's. The manager tells us he was backing up the car and didn't notice the truck behind him had its lift down -- so when he hit the lift and tried to pull forward, it ripped the bumper almost clean off.

It all went down in Hollywood ... right after Sitch left Playhouse nightclub with a few members of his crew. The "Jersey Shore" star rolled into a waiting SUV and took off ... but moments later, the car was stopped on the side of the road ... next to an LAPD squad car with flashing lights.

It's unclear why the police got involved -- but both The Situation and his friends got out of their SUV and had a friendly exchange with the officers ... who never got out of their squad car.

As we first reported, Susan was set to sing "Hallelujah" on the show tomorrow. But a rep for the show confirmed to TMZ she won't be appearing this week -- no word yet on rescheduling.

A source tells us Susan missed a flight to L.A. today. She was supposed to tape her performance on the "DWTS" set this evening.

We're told host Tom Bergeron will address the issue on tonight's show.

Sources close to the show tell TMZ Audrina tweaked her ankle during rehearsals yesterday and she was tended to by on-set physicians. Not to worry though ... we're told it's just a minor sprain and Audrina is "pushing through."

Count yourself lucky, Audrina ... it could have been worse.

Sources tell us Boyle is scheduled to perform on Tuesday's live show -- and unlike her experience on "Talent" ... we're guessing she'll make "Dancing" producers clear the song she wants to sing -- "Hallelujah" by Leonard Cohen -- before she touches down on American soil.

As TMZ first reported ... Boyle was blindsided moments before she was supposed to perform on "America's Got Talent" last month ... when she found out Lou Reed wouldn't give her permission to sing his hit "Perfect Day." Boyle was so devastated, she broke down in tears and caught the first plane back to the U.K.

"DWTS" producers tell us, "While we respect the feelings of our celebrities and dancers, we don’t feel Bruno should be expected to apologize for doing his job.”

As you probably heard, Bruno told Bolton that his jive was the worst jive he's ever seen -- and Bolton responded by calling the judge "inappropriate and disrespectful."

But show producers note, "Bruno’s role as a judge is to give his honest opinions on the quality of the dances he’s judging, which is what he did in this case."

So why are the nachos important!?

Alaska officials have reportedly launched an investigation into Bristol's night out -- because state law would only allow the 19-year-old to be inside Rumrunner Bar and Grill if it's been designated as a bona fide restaurant, and she was there to eat.

A state investigator is reportedly looking into a "Dancing with the Stars" segment that 19-year-old Bristol taped inside Rumrunner's Old Towne Bar and Grill on Thursday.

But a source extremely close to Bristol tells TMZ ... "The place is also a restaurant ... so under 21 is allowed under Alaska law if accompanied by a person over 21, which she was." Bristol was with her partner Mark Ballas during the segment -- and he's 24.

And here's the rub -- our source is adamant, "Bristol had nachos only."

So far, the Alaska Department of Public Safety has no official comment on the situation.