Update 3:10 p.m.

Authorities say the building was ventilated. It is now safe and people were allowed back in.

There was no information available as to what the exact cause was.

Original 1:25 p.m.

PORTLAND — A building on Congress Street has been evacuated, according to the Portland Fire Department.

Crews are currently at 415 Congress St. investigating a carbon monoxide problem, a dispatcher said. At this time, it is unsure when people will be able to re-enter the building.