UFC's Desmond Green Arrested For DUI Manslaughter After Deadly Crash

UFC fighter Desmond Green was arrested for DUI manslaughter Tuesday after he allegedly caused a 5-car crash that killed 2 women back in August ... and officials claim he had alcohol and drugs in his system and cocaine in his vehicle.

29-year-old Green is facing multiple charges after he allegedly lost control of his 2011 Dodge Durango on I-75 and swerved into a semi truck on August 18.

So, why did it take so long to arrest Green? Officials say they conducted a massive investigation that took months to complete. And now, they feel they have enough information to successfully prosecute Green.

Here's what cops say happened ...

The initial collision started a chain reaction ... with Green's car striking several vehicles, killing a 67-year-old woman and a 76-year-old woman. Cops say 2 others were also seriously injured.

Cops say Green sustained minor injuries from the incident.

According to the police report, witnesses told cops Green threw a container over the highway barrier after the crash ... which cops say was a metal grinder with weed inside.

The report also says Green -- who wasn't wearing a seat belt at the time of the crash -- had a bag of cocaine in the front seat of his car.

Cops claim Green showed signs of being drunk -- he had slurred speech and smelled like booze -- and toxicology tests showed he had alcohol and drugs in his system.

Green is now facing a slew of criminal charges -- including multiple felony manslaughter counts -- and faces serious prison time if convicted.