About 150 people have been evacuated from their homes in Montgomery County because of a mysterious odor.
Crews were dispatched around 5:45 p.m. Sunday to the 4200 block of North Gorski Lane in Skippack Township.
The odor is due to a "volatile organic compound" coming from the sump pumps in the basements, officials said Monday.
The Montgomery County Department of Public Safety said the county hazardous response team, state Department of Environmental Protection and federal Environmental Protection Agency are working to identify the compound involved.
About 150 people were initially evacuated to Skippack Elementary School. The Red Cross said it helped shelter four families, for a total of 10 people who had no place to go for the night.
The Red Cross' partners at Red Paw are assisting to shelter the pets of these families.
One homeowner said it was his wife who initially discovered the smell.
"My wife called and said she had a chemical smell in the house and called me. I came home and walked in the house. As soon as I walked in, I could smell it, and then we called 911 and they came out and advised us to go get my wife and kids checked at the hospital," said Matt Logan.
The incident was first believed to be a possible gas leak, but two energy companies in the area said their systems were operating normally.
Residents are being asked to contact the township to have their homes tested for the presence of the compound before returning home.