ANN ARBOR, Mich. -

The city of Ann Arbor is on high alert after intruders broke into four homes.

The four recent break-ins happened in neighborhoods along US Highway 23.

According to police, all the homes had one thing in common: They were for sale. They were also all broken into through rear entrances. It’s not clear what was taken from the homes.

Police are urging residents to be mindful of empty houses and to call if they see anything suspicious.