EL CAJON, Calif. -- Authorities Monday warned people who live along several Granite Hills-area streets about a three-month series of residential burglaries in the neighborhood.

Residents of 15 homes on Mahogany Drive and Spanish Oak Place have been victimized by completed or attempted home-invasion thefts since mid-October, most recently last week, according to the El Cajon Police Department.

Late Friday and early Saturday, two burglaries and five failed break-ins took place in the area, ECPD Lt. Steve Shakowski said.

The crimes have generally occurred while residents were home, according to investigators. Items typically stolen include wallets, purses, cell phones and other easily carried valuables, Shakowski said.

During the most recent burglaries, several victims heard unusual sounds but failed to notify the authorities, thinking the noises were harmless.

"The El Cajon Police Department encourages members of this community to notify us if they see, hear or suspect anything unusual taking place in or around their residences, as we are concerned over the potential for a violent confrontation between the (burglar) and potential victims," the lieutenant said.

Detectives believe the perpetrator may be a friend or relative of an area resident and a frequent visitor to the neighborhood, Shakowski said.