Police and car insurers say thieves are using laptop computers to hack into late-model cars’ electronic ignitions to steal the vehicles, raising alarms about the auto industry’s greater use of computer controls.

The discovery follows a recent incident in Houston in which a pair of car thieves were caught on camera using a laptop to start a 2010 Jeep Wrangler and steal it from the owner’s driveway. Police say the same method may have been used in the theft of four other late-model Wranglers and Cherokees in the city. None...