Chicago police are warning commuters on the South Side about a group of men who robbed several people on CTA property in July.

In each incident, three men in their 20s approached the victim and pretended to ask for a lighter or offered to sell loose cigarettes, then attacked them and stole their property, Chicago police said. At least one of these robberies happened on a Red Line train.

The robberies happened:

Between 8 p.m. and 8:30 p.m. July 7 in the 200 block of West 63rd Street near the 63rd St. Red Line station;

About 2 a.m. July 21 in the first block of West 69 th Street near the 69 th St. Red Line station;

Street near the 69 St. Red Line station; About 2:50 p.m. July 26 in the 6600 block of South State Street; and

About 7 p.m. July 31 in the 700 block of East 65th Street.

Anyone with information about these robberies is asked to call Area Central detectives at 312-747-8380.