An underground fire caused a buildup of carbon monoxide Monday morning, sickening at least two people and forcing dozens of others to leave their homes, officials said.

The fire was reported around 6:45 a.m. as electrical wires burning in a manhole at North 2nd and Walnut streets in Reading, said Chief David Hollinger, Reading Fire Dept.

Firefighters worked about a half-hour to control the underground fire.

In the meantime, smoke and carbon monoxide made their way into some homes in the 200 block of Pear Street, Hollinger said.

Firefighters went door to door and found a high level of carbon monoxide in about a dozen homes, although 60 were evacuated as a precaution, Hollinger said.

A cooling station for evacuees was set up at Lauer's Park Elementary School.

At least two people reported feeling sick at the scene, but they refused treatment.