Police are asking business owners to bolster their security systems after a series of commercial burglaries were reported at businesses across the North Side.

In two of the burglaries, someone shattered the glass door of the business and stole property from inside, Chicago police said. In the third, the burglar tried and failed to force open a door.

The three incidents happened:

· About 3 a.m., May 15 in the 4000 block of North Milwaukee Avenue in Portage Park;

· About 8:30 a.m., May 26 in the 1700 block of West Fullerton Avenue near the Lathrop Homes; and

· About 5:30 a.m., June 4 in the 6300 block of North Lincoln Avenue in North Park.

Police are searching for two burglars in the Portage Park incident who used a silver Ford pick-up truck to escape, police said. They were described as two males between 5-foot-8 and 6-feet and weighing between 150 and 170 pounds.

The offender in the Lathrop Homes burglary was described as an 18- to 22-year-old man on a bicycle, standing between 5-foot-6 and 5-foot-8 and weighing about 175 pounds, police said.

No description was given for the burglar in the North Park incident, besides that he was a male driving a gray pick-up truck.

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