New Castle residents began noticing the smell Nov. 1 in the city about 45 miles northwest of Pittsburgh. 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.
A spokeswoman for the Pennsylvania Department of Environmental Protection says on-site monitoring didn't detect any hazardous substances in the air.
But tests on air samples to determine what's causing the smell will take weeks to complete. The DEP is also testing wastewater to determine whether it's causing the smell.
