Updated 02/15/11 – 4:44 p.m.

CHICAGO (CBS) — Police are investigating after a woman was sexually assaulted in an alley on the city’s Far South Side.

The young woman said she was attacked in an alley near 120th Street and Union Avenue in the West Pullman neighborhood at about 11 p.m. Monday, police said. She was taken to Roseland Community Hospital for treatment.

Lavita Grayce heard the victim’s cries for help.

“I heard a boom boom boom and a door slam and then I heard like three screams and then I ran in the house, came back out, police was everywhere,” Grayce said.

Chicago police were investigating, but the case also had the attention of Riverdale police, who are looking for two suspects wanted for two sexual assaults in January. Those attacks happened one day apart. Both victims were 17 years old and the sketches of the two suspects look similar.

Considering the two attacks in Riverdale and the one in Chicago happened just a few miles apart and under similar circumstances, Riverdale Police Chief William McHenry wanted to know if the Chicago rape was connected to the attacks in Riverdale.

“We’re working with all the suburban agencies as well as Chicago police to try to find out what is going on with this series of sexual assaults … and if they’re connected,” he said.

There were reports that Calumet Area police detectives were questioning two men about the West Pullman attack on Tuesday morning, but police later said those two men were released because the victim could not identify them as her attackers.

Chicago police had no description of the suspect, but the town of Riverdale is circulating a sketch of a suspect they say sexually assaulted two 17-year-old girls at 142nd and Wallace. Officials say they have reason to believe the suspect was the same man that had been questioned by Chicago police for the Monday night attack.

CBS 2’s Dana Kozlov and The Sun-Times Media Wire contributed to this report.

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