CHICAGO — CTA riders should be on the lookout after a series of incidents in which bus windows on the South Side have been hit with BB gun pellets, according to a Chicago Police alert.

Earlier this month, there were four similar incidents in which buses were damaged in BB gun or pellet gun attacks. The incidents occurred in the following locations and times, police said:

• In the 7900 block of South South Chicago Avenue on Oct. 5 at 10:10 p.m.

• In the 7900 block of South Perry Avenue on Oct. 9 at 2:30 p.m.

• In the 7900 block of South Dorchester Avenue on Oct. 9 at 2:30 p.m.

• In the 13220 block of South Ellis Avenue on Oct. 9 at 2:30 p.m.

No one appears to have been hurt in the shootings. The alert did not indicate whether police believed the attacks were related, and no description of a suspect or suspects was released.

Anyone with information is asked to call police at 312-747-8273.