PHILADELPHIA (CBS) — Residents were evacuated after carbon monoxide was detected at a Center City apartment building.

Firefighters responded around 9 p.m. Monday at the Casa Farnese Apartments near 13th and Lombard Streets.

Residents were evacuated to the lobby as firefighters went through the building.

The executive property manager says the problem was traced to a malfunctioning boiler which was shut down by the building’s contractor.  Two additional boilers continued to operate without a problem providing continued heat to the building.

The American Red Cross responded to help the 300 residents affected.

No injuries were reported.

The Fire Department and PGW cleared all residents to return to their apartments by 11:15 p.m.