A man was transported to the hospital with head injuries on Saturday morning after his motorcycle crashed in Allston, police said.

The man was riding west on Brighton Avenue at about 2:30 a.m. when the crash occurred. Witnesses said the man had just stopped at a traffic light at the corner of Allston Street and was beginning to accelerate when his motorcycle skidded sideways, ejecting him onto the street. The motorcycle came to rest on top of the man after the crash, witnesses said.

The extent of the man’s injuries is unknown. Police at the scene said that the victim was bleeding from the head and that his injuries were serious.

Witnesses said that at least one other motorcycle rider was stopped at the traffic light near the victim immediately before the incident.

The man was wearing a helmet when the crash occurred.

No other injuries were reported. The cause of the crash remains under investigation.