The Princeton Police Department is warning residents not to leave their cars running and unattended in their driveways. A series of thefts of idling cars in Hamilton Township, followed by one in Princeton on Friday, prompted the warning.

A 2011 Audi A4 was stolen from the driveway of a home on Leicester Court around 7:30 a.m. Friday, according to information from Sergeant Steven Riccitello. The owner of the car had started the vehicle and left it running to warm it up. He then went back into his house.

According to police, the car’s owner saw a black male drive away with the Audi, which was valued at $36,000. The man, described as having an athletic build and wearing a black wool coat with a red scarf, got out of a newer model blue Mercedes, possibly C class, and drove away with the Audi.

Four idling cars were stolen from driveways in Hamilton on Thursday morning. No arrests have been made.