Residents of 150 suburban Philadelphia homes are being allowed to return as their houses are tested after a voluntary evacuation overnight due to a mysterious odor.
Officials are awaiting lab results to try to identify the substance responsible for Sunday evening’s problem in the neighborhood in Skippack.
Officials have identified basement sump pumps as the origin but have not been able to pinpoint the cause.
Authorities say they believe a type of organic substance emitted as gases from thousands of products was responsible. The products include paints, lacquers, cleaning supplies and stored fuels. But officials say there have been no signs of illness.
Authorities had tested about half of the homes by noontime Monday and said they were safe for residents to return with little or no evidence of contamination.