Police in four eastern Contra Costa County communities are investigating a string of home burglaries that they said are being carried out by groups of teens.

On Tuesday, the police departments in Antioch, Brentwood, Oakley and Pittsburg issued a warning on social media about the burglaries.

According to police, groups of juveniles enter homes through unlocked doors, sliding glass doors or unsecured windows. In some cases, the burglars remove window screens to gain entry.

"They appear to be looking primarily for vehicle keys, which has unfortunately led to several stolen vehicles," said a statement from the Pittsburg Police Department.

Residents in the four cities are being urged to keep doors locked, windows secured and to protect their car keys, particularly during overnight hours. Police suggested placing car keys in a "secure, less visible area", away from entryways, kitchen counters or tables.

Police said they are working with the Contra Costa County District Attorney's Office on the investigation.