CHICAGO (CBS) — Police have issued a business alert along the southern lakefront after a series of armed robberies targeting fast food delivery drivers over the past month.

CBS 2’s Mike Puccinelli reports that the incidents all happened in the Prairie District, particularly the Hyde Park neighborhood.

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Chising Lam, an immigrant from Hong Kong who delivers pizza for a living, might be working one of the most dangerous jobs in the area right now.

Police said delivery drivers in the Prairie District have been targeted by an armed gunman. In the past month, several have been robbed at gunpoint. It’s gotten so bad that police have started alerting businesses.

In each of the robberies, the perpetrator placed a phone order asking for a delivery and robbed the driver when he or she arrived.

The robbery spree has made Lam change the way he delivers food to certain areas of the city.

“In the nighttime, I will never go there,” he said. “In the daytime I will go there, but I will stay in the car and let the customer get the pizza.”

He has good reason to do so, because a few months ago his colleague Best Yooden learned just how dangerous delivering pizza can be.

Yooden, a black belt in Tae Kwan Do, said he was punched in the back of the head, then six or seven young men jumped and robbed him in the courtyard of an apartment complex on South Drexel Avenue.

“They tried to make sure I didn’t get up, and they keep on punching and kicking me as well,” he said.

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Yooden said his ordeal lasted several minutes and his face was swollen afterward.

“I [couldn’t] even use my right eye … because it was swollen and this eye was kind of closed,” he said.

Atino’s Pizza manager Samanatha Montiel said that just two weeks ago another one of her drivers was attacked and tackled to the ground.

At least one driver from a nearby Domino’s was also attacked by robbers.

Montiel said she’s worried for her workers.

“They’re scared sometimes when it is the night and the weekends,” she said.

The robber is described as an African-American male between the ages of 17 and 25, standing 5 feet 8 inches to 6 feet tall, weighing 150 to 200 pounds, and wearing dark clothing. He was armed with a handgun in the incidents.

Police advised business owners to ask customers to leave their porch and vestibule lights on for the driver, while delivery drivers should leave right away if they realize they have been sent to an address that is vacant or abandoned. Suspicion is also warranted if a caller expects change for big bills.

Drivers should also contact customers again when they arrive and should not exit their vehicles until they see the customer or customers in person, police advised.

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Anyone with information on the crimes is asked to call the Wentworth Area Detective Division, at (312) 747-8382.