PHILADELPHIA—Residents at a high-rise building for senior citizens have been allowed to return to their apartments after being evacuated to the lobby because of concerns about carbon monoxide. reports ( that firefighters detected elevated levels of carbon monoxide at the Casa Farnese apartments in Center City around 9 p.m. Monday. Residents were sent to the lobby until they were allowed to go back to their apartments.

Red Cross spokesman Dave Schrader says about 300 people were affected. He says residents returned to their homes late Monday night.