By Suzanne Monaghan

TINICUM Twp., Pa. (CBS) — An office complex building in Delaware County was evacuated today after reports of a strange odor that sickened several people.

Several people reported feeling ill and 16 were taken to area hospitals, but are expected to be okay, according to an official with Delaware County Emergency Services.

Some were experiencing shortness of breath and chest pains. It happened around noon at International Plaza Complex in Tinicum Township.

Investigators say a problem in the heater room was to blame and caused a carbon monoxide leak. It primarily affected workers on the 4th and 5th floors of the 6-story building.

Crews spent much of the afternoon working to ventilate the structure.