BEDFORD, Mass. (AP) — One person was critically injured and four others were hurt when a wooden wall at a home under construction in Massachusetts collapsed on them Wednesday morning, authorities said.

The construction workers were trapped in the collapse in Bedford at about 7:30 a.m., according to a statement from town officials.

First responders arrived on the scene to find a bystander administering first aid.

After they were extricated, all five were taken to the hospital, one with what are believed to be life-threatening injuries, authorities said. All five were men but no other information about them was released.

A Bedford firefighter was also treated for injuries at the scene.

The workers were constructing a room above a three-car garage and interim Bedford Fire Chief Paul Sheehan estimated the wall was at least 20 feet (6 meters) long.

The town’s building inspector believes the collapse was due to improper construction techniques.

The federal Occupational Safety and Health Administration also responded to the scene to investigate and will make a final determination on the cause, Sheehan said.

Bedford is about 15 miles (24 kilometers) northwest of Boston.