The Pennsylvania Department of Environmental Protection is warning residents about dangerously high levels of radon.
Radon is a naturally occurring radioactive gas that may cause up to 21,000 lung cancer deaths a year nationally.
A spokesperson for the agency says he could not share which area is affected.
The agency says at least one home has a radon level 25 times higher than recommended. In a letter sent to one resident, the agency says Pennsylvania generally has "some of the highest radon values in the country."
The state is providing grant money to the American Lung Association in Pennsylvania for free radon tests kits to Hampden Township residents.