Why does a Pennsylvania city smell like cat urine?

NEW CASTLE, Pa. -- Residents are hoping air sample tests can explain why their western Pennsylvania city smells like cat urine.

New Castle residents began noticing the smell Nov. 1 in the city about 45 miles northwest of Pittsburgh. Weeks later, the New Castle News says the smell is still lingering near a sewage treatment plant in the city's Mahoningtown neighborhood.

State environmental officials don't believe the odor is harmful, but they don't yet know what's causing it.

Amanda Witman, a spokeswoman for the Pennsylvania Department of Environmental Protection, says on-site monitoring didn't detect any hazardous substances in the air.

But tests to determine what's causing the smell will take weeks to complete. The DEP is also testing wastewater to determine whether it's responsible for the odor.