A construction worker suffered a life-threatening head injury when he fell from the roof of an Overlook Lane home on Tuesday afternoon, said Robert W. Kowalski, area director of the Occupational Safety and Health Administration, which is investigating the incident.

"It's my understanding that when he fell he may have hit his head on a very large object on the ground. It might have been a rock," Kowalski said Wednesday.

The man, initially identified only as a Bridgeport resident, was working for a roof subcontractor on the construction job, police said.

Police, fire and Westport EMS personnel were dispatched to the scene when the incident was reported about 2 p.m. The worker was transported to Norwalk Hospital. Police have not identified the victim.

Kowalski said this was the fourth person to fall from a roof this week in Fairfield, New Haven and Middlesex counties.

"Falls are a very common issue with construction, whether it's residential or commercial."

The other four incidents resulted in a broken arm, a broken ankle, head lacerations and arm contusions, respectively.