Chicago police are warning residents of catalytic converter thefts reported in June in Jefferson Park on the North Side.

In each incident vehicles were parked on the street overnight, according to a community alert from Chicago police.

The incidents happened:

In the 4800 block of North Mason Avenue;

In the 5900 block of West Foster Avenue;

In the 5700 block of West Avenue;

In the 5400 block of West Giddings Street;

In the 5300 block of West Cornelia Avenue;

In the 6000 block of West Seminole Street;

In the 5600 block of North Mason Avenue;

In the 5300 block of North Northwest Highway; and

In the 5100 block of West Cornelia Avenue.

Police did not offer a description of the possible offender but warned that they may be armed.

Anyone with information about these thefts is asked to call Area North detectives at 312-744-8263.