ELMHURST, Ill. (WLS) -- Elmhurst police are warning residents take their keys out and lock their cars after an uptick in car thefts.Calling it a "new crime trend," police say thieves are stealing unlocked vehicles with keys or key fobs left inside. Over 100 vehicles have been stolen and more than 200 vehicles have been burglarized, police said.In most reported cases, the stolen vehicles have been identified as high-end unlocked cars parked overnight in residential driveways, police said."This crime trend has been occurring since May in targeted areas close to major highways. Cities that have been affected include Lake Forest, Lake Bluff, Wilmette, Highland Park, Glencoe, Glenview, Winnetka, Northbrook, Deerfield, Hinsdale, Bolingbrook, Naperville, and most recently Elmhurst, where two vehicles were stolen," an Elmhurst news release said.Elmhurst police are alerting residents of the importance of locking car and garage doors. Leaving keys, key fobs, wallets, or any other valuables in your car puts your car at a high risk of being stolen, police said. Installing motion sensor lights in driveways and the front of homes is recommended as a deterrent, police said."If the thieves did not find the keys, they stole what they could," Elmhurst Police Chief Michael Ruth said.Clarendon Hill police sent out a similar alert, saying "suspected gang members from the city" are targeting the suburbs. Clarendon Hills police say six cars in Hinsdale and one in their town have been stolen.Residents in Glen Ellyn were also warned by police to secure their vehicles after a rash of car thefts.In most cases, the cars were unlocked with the keys inside. Thieves also used garage openers inside the cars to get into homes and search for the keys.The crimes usually happened during overnight hours, with purses and wallets also taken.