PORTLAND — Several city fire trucks and ambulances were sent to 100 Federal Street this morning after two men, who had been working on a basement boiler, became ill.

Deputy Fire Chief Bill Flynn said a boiler technician had gone to the basement with a building maintenance worker when both men started feeling dizzy and nauseous.

“Their symptoms presented themselves as carbon monoxide (poisoning) but our readings could find no evidence of it,” Flynn said.

Flynn said firefighters took carbon monoxide readings but could find no trace of the odorless gas which has the potential to be lethal.

As a precaution, the boiler technician was transported by ambulance to Maine Medical Center. Flynn said firefighters are uncertain what caused both men to become ill.

The call came into the fire department at 10:52 a.m.