CHICAGO (CBS) — Congressman Bobby Rush has asked the FBI to take over an investigation into 55 unsolved murders of women in Chicago.

CBS 2 Investigator Pam Zekman has reported that many of those cases have led some to believe that a serial killer is responsible for the killings.

“I am writing you today with a deep sense of urgency and frustration,” Rush wrote in the letter to FBI Director Christopher Wray. “It has become evident that part of the reason these crimes remain unsolved is due to the backlog in evidence processing by the Illinois State Police Forensic Science Laboratory System.”

“It is apparent that the lack of resolution to these heinous crimes demands further involvement by the federal government, specifically the FBI,” said Rush, who cited Zekman’s reporting in his letter.

Since 2001, several bodies have been found in vacant lots, abandoned buildings and alleys. Some were dumped in garbage cans, and some even set on fire; all of them strangled.

The 2 Investigators asked the Murder Accountability Project to review more than 50 unsolved strangulation and asphyxiation cases dating back to 2001. The group — known as MAP — has a knack for finding patterns in unsolved murder cases using a computer algorithm.

“It’s essentially a serial killer detector, and for many years our algorithm has been signaling red alert about a series of strangulations in Chicago,” said Murder Accountability Project Director Thomas Hargrove.