Greenwich police are warning drivers to lock their cars after more than a dozen vehicle thefts around town.

Police say a car thief can get behind the wheel and drive away within seconds.

Some victims make it especially easy by leaving the cars unlocked and the keys inside. And police say the burglaries are being committed by loosely knit groups and can happen anywhere.

"My husband and my children and I were shopping at Brooks Brothers right here in town," says Greenwich resident Carol McGuire. "And we parked right next to a car. It was a convertible, beautiful. I think it was an old Mercedes or something with the keys literally in the cup holder."

That Mercedes would be the ideal target for car thieves, police say. 

Lt. John Slusarz, of the Greenwich Police Department, says thieves approach each car they pass, testing to see which are unlocked before capitalizing with crimes of opportunity.

Greenwich police say they've received 13 reports of stolen cars so far in November -- twice as many as in October.

"Lock your cars," McGuire says. "Take your keys with you."