Portland, ME – Three people were taken by ambulance to a hospital and firefighters evacuated two floors of a 10-story office building on Marginal Way in Portland on Friday after a possible carbon monoxide problem.

Staff members at InterMed, which occupies the top four floors at 84 Marginal Way, contacted the Portland Fire Department twice on Friday, first around 9 a.m. and again at 11:30 a.m., said Assistant Fire Chief Keith Gautreau.

Workers on the seventh and eighth floors of the healthcare provider had symptoms of dizziness, nausea and headaches during both calls, Gautreau said.

As a result of the first call, the fire department took one person to Maine Medical Center in Portland and evaluated many more.

“We went through the building with our monitors,” Gautreau said. “We evaluated close to 20 people. Some of them had elevated levels of carbon monoxide, but nothing that was life threatening or even critical.”

But firefighters could not detect any problem on their meters inside or a source of the problem and let people go back to work as a private heating, ventilation and air conditioning crew continued to work inside.

During the second call, firefighters took two more people to the hospital and evaluated another 50 workers, many with the same symptoms. Firefighters who walked through the building even evaluated each other and found some of them had elevated levels of carbon monoxide in their systems too, Gautreau said.

“It’s really kind of a mystery,” he said. “We’ll do some follow up for sure.”

A law firm, Drummond Woodsum, occupies two floors of the building, but no one there had any symptoms. A pharmacy on the ground floor also had no problem. The other floors are occupied by a parking garage.

Dan McCormack, InterMed’s chief executive officer, said that a fourth InterMed employee went to a walk-in clinic to be treated for symptoms and had blood tests done. Everyone else was allowed to go home for the rest of the day.

“We just found out that all four had carbon monoxide levels that were within normal levels. We don’t know at this point,” McCormack said. “We decided to close for the afternoon out of an abundance of caution.”

InterMed staff members contacted as many patients as possible to tell them that appointments had been canceled for the day, but some who arrived had to be turned away, he said.

McCormack said the evacuation and cancellations Friday were a disruption to patients, but that he would rather err on the side of caution than put anyone at risk.

InterMed’s Portland office does not see patients over the weekend, so McCormack said he hoped that the workers assessing the ventilation system would be able to solve the mystery before Monday.