Police in Jefferson County are investigating a series of vehicle thefts with something in common: They all happened while the vehicles were running to warm up.

KMOV-TV reports that nine vehicles were taken over the past few weeks. The latest was a 2007 Chevrolet Silverado stolen Monday morning near Arnold. That pickup has been found a police say they are investigating a person of interest.

Jefferson County Sheriff's Department Lt. Garry Higginbotham says it's not clear if the thefts are related. An investigation continues. In the meantime, officials warn residents against starting a car and leaving it unattended to warm up.