Residents are looking for answers about a strange problem that is afflicting the city of New Castle in Pennsylvania in the US.

Air samples are being collected to try and find out why the city smells like cat urine.

People began noticing the smell in early November but 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.