Two people are dead after a hit-and-run driver plowed into a group of cyclists ... dragging one of the victims over a mile.

The fatal collision went down on Saturday night at around 10 PM in Montclair, California ... KTLA reported.

Neighbors said a group of young men -- possibly teens -- were riding bikes together when a gray Honda reportedly slammed into them.

The victim who was dragged by the car was left in a residential neighborhood. It's unclear if the victim was one of the 2 killed in the incident.

The pics of the scene are pretty graphic ... with one of the deceased covered with a blanket and bikes strewn across the road.

So far ... none of the victims -- or a possible suspect -- have been identified by police.