BRUNSWICK – Four people were injured Thursday in an accident at a construction site where workers were building a new medical office center.

Workers were putting in roof trusses on the building on Medical Center Drive, off Bath Road, when one of the trusses broke and brought down 12 others, according to Fire Chief Gary Howard. He estimated that each truss weighed about 500 pounds.

Brunswick police said Shane Lessard, 27, of Waterville was taken to Maine Medical Center in Portland. Dave Perry, 21, of Winslow, Mark Whittaker, 21, of Dixmont, and Blaine Hamlin, 22, of Waterville were admitted to Midcoast Hospital in Brunswick.

Police said the four men worked for Mapleleaf Construction of Fairfield. The Occupational Safety and Health Administration was investigating the accident.