9:00 AM PT -- According to cops, Danny was found with 2 vertical lacerations on his forearm. We're told police are now treating it as a possible suicide.

Danny Dias, who starred in season 13 of MTV's 'Road Rules,' has died and it appears drugs were involved ... TMZ has learned.

We're told Dias was at his Brooklyn apartment Saturday with a friend. Law enforcement sources say the friend told them he saw Dias take what he believed was LSD and mushrooms. The friend says Dias freaked out, ran in his room and that was the last the friend saw of him.

We're told the friend left the apartment and over the next 2 days called Dias, getting no response. The friend became concerned and on Monday called 911 for to get a welfare check on Dias. First responders had to force their way in, and found Danny dead in the room.

Dias appeared on the 2004 season.