RUMFORD — A faulty furnace is to blame for thick smoke and heavy levels of carbon monoxide at the Sun Journal’s Rumford bureau offices on Sunday.

Deputy Chief Richard Coulombe, of the Rumford Fire Department, said that crews were dispatched to the Congress Street office after a cleaning lady called 911 Sunday morning at around 10:45 a.m. and reported smoke and a weird smell in the building. The woman was lightheaded as a result of the incident, but declined medical treatment and was doing better after getting into the fresh air, Coulombe said.

Firefighters equipped with air masks and tanks detected minor levels of carbon monoxide at the entrance to the office building, but much higher levels upon reaching the furnace in the basement, Coulombe said. He explained that a reading of about 35 parts per million is enough to set off a carbon monoxide alarm, and that the readings in the basement were around 40 parts per million.

Firefighters aired out the smoke and carbon monoxide from the building and cleared the scene shortly before noon.

The fire department turned off the furnace and told the staffs of the Sun Journal bureau and the Rumford Falls Times that the furnace must remain off until it’s repaired.