Tracy Morgan caused a lengthy delay at the Knicks game Monday night ... after he upchucked all over the floor.

The troubling scene unfolded during the first half of New York's tilt with the Miami Heat at Madison Square Garden ... when the comedian suddenly got sick in his courtside chair.

Images taken by fans at the arena show Morgan vomited near his feet ... and so much came out of his stomach, some of the contents actually splashed onto MSG's playing area.

The game was halted for several minutes as medics raced to tend to the 56-year-old.

Morgan -- a Knicks superfan -- was put into a wheelchair and pushed out of the area. He seemed visibly distressed as he held a towel to his face. Spectators stated they could see blood coming from his nose as he exited.

No word at all yet on what caused the medical episode ... but the Knicks vs. Heat game has resumed. New York currently leads 109-84.

Story developing ...