WINTHROP -- A fire scare forced an evacuation of Winthrop Medical Center on Main Street for more than two hours Friday afternoon.

A medical center staff member pulled a fire alarm after white smoke began flowing from the facility's heating vents on the third floor of the building, Winthrop Family Practice coordinator Beth Corey-Smith said.

Five patients and 45 staff members were forced to evacuate from the building, which housed the now-defunct Carleton Woolen Mill. Winthrop Medical Center, a unit of MaineGeneral Health, occupies the second and third floors of the brick building.

Winthrop police closed Main Street from Bowdoin to Green streets while firefighters responded to the scene.

Staff members said a white, odorless smoke began wafting into the hallways at approximately 12:30 p.m.

Fire officials and an electrical contractor inspected the facility and, by using a computer system monitoring the building's electrical system, determined a heat pump ruptured, causing the white smoke to flow from the third floor vents, Winthrop Deputy Fire Chief Bob Ouellette said.

The smoke was the result of oil and freon being expelled through the vents.

"It didn't burn and we're very happy about it," Ouellette said.

Winthrop Deputy Fire Chief Dave Currie said the firefighters at first had difficulty pinpointing the cause of the smoke.

"Nothing was overheated. There were no hot spots," Currie said. "It's a big building to go looking through every room."

The cause became apparent once the electrical contractor used the building's computer system to monitor the heating pumps.

Fire departments from Fayette, Manchester, Monmouth, Mount Vernon, Readfield and Wayne assisted Winthrop firefighters at the scene.

Staff members and patients were cleared to return to the building shortly before 2:30 p.m. Main Street reopened shortly before 2 p.m. after it closed for approximately 11/2 hours.

Corey-Smith said staff members were well rehearsed in the medical center's evacuation plans.

"It is due to the fire drill training of staff everyone got out," Corey-Smith said. "Everybody knows what to do."

The evacuation was simple in part because a number of employees were out of the building at lunch when the scare happened, staff members said.

Corey-Smith said the staff members still in the building visited each room to make sure patients were evacuated. Staff members posted fluorescent orange magnets on the doors of empty rooms so firefighters would know the rooms were evacuated.

Winthrop Medical Center houses the family practice, a pediatrics practice, an orthopedics office, imaging facilities and a laboratory.

Matthew Stone -- 623-3811, Ext. 435

mstone@centralmaine.com