North Wales Police believe thieves are "scouting" around areas of Flintshire looking for expensive cars to steal. The latest incident happened just before midnight on Saturday when thieves raided a property on the outskirts of Mold.
They stole a briefcase from the hallway and a �30,000 silver Mercedes C270 Cdi Elegance from the drive.
It is the latest in a series of burglaries which have resulted in high-powered cars being stolen from homes in Hope, Carmel, Connah's Quay and Holywell over the last few weeks.
DS Kevin Leech from Mold CID said officers are taking the robberies seriously.
"I'm convinced these thieves are scouting around in the area looking for expensive cars on driveways," he said.
"I believe they are then returning to the property and using an implement to get access to the premises to get the vehicle's keys."
Householders have been warned not not to leave keys lying around within easy access of their letterbox.
Anyone with information about these incidents is asked to contact police on 0845 607 1001.