Firefighters called to investigate an irritating odor evacuated residents of an apartment at 645 S. 20th St. Thursday night.

Lincoln Fire and Rescue Deputy Chief Pat Borer said firefighters were called at about 7:30 p.m. and evacuated the apartment building. They checked the building for harmful chemicals and gases but didn’t find anything.

It was not a gas leak, Borer said. Firefighters thought it might be pepper spray at first.

They ventilated the building and let residents return, but were called back after a resident called to say the odor was still strong in her apartment, Borer said.

Firefighters were continuing to investigate until shortly after 9:30 p.m., when they determined the cause — hot peppers.

“They did a little more investigation and found one of the second-floor residents was cooking peppers, hot peppers, and that was the source of the fumes in the air that everybody was breathing,” Borer said.

The American Red Cross relocated three families for the night.