The man accused of being the “Cleveland Strangler” lived for years with the niece of the city’s mayor in a stinking house where police have found 11 corpses.

The revelation raises questions about why police took so long to arrest the former US marine, a convicted rapist whose home reeked of rotting bodies.

Lori Frazier, a niece of the Mayor, Frank Jackson, said that she still considered herself to be the girlfriend of Anthony Sowell, who was released from a 15-year prison sentence in 2005. “He came out from the penitentiary on June 23. Me and him hooked up on July 7, and I have been with him ever since,” she told reporters in Cleveland, Ohio. “I want to know why, why would he do this,” she said. “He took care of me.”

Ms Frazier, a drug user, said that Mr Sowell explained away the pungent smell of decaying bodies in the house by blaming his stepmother downstairs and, when she moved out, a sausage factory next door.

She said that the pair took drugs together until she moved out last year in an attempt to kick the habit. Ms Frazier’s relationship with Mr Sowell will have left her uncle in a precarious position. Mr Jackson, who was elected to a second term last week, has promised to examine the police response, but only after the murder investigation has been completed.

Zach Reed, a councillor who filed a complaint about the odour two years ago, has called for a federal investigation into the police response. Police insist that an officer who went to the house on September 22 to make a random check on the sex offender was not entitled to enter the house, despite the stench of death.

When a naked woman fell from a window of the house hours later, and was found by neighbours being choked by Mr Sowell, police reportedly arrived late, and again did not enter the building.

The coroner has identified seven of the victims. They are all black women, all mothers, aged between 31 and 52, with criminal records and a history of drug abuse.

A woman who escaped said that she had thought Mr Sowell was a “civilised person” when she first went upstairs to have a beer with him in April. “I’m sitting on the corner of the bed and then he just leaped up and came over and started choking me,” said Tanja Doss. “He said, ‘If you want to live, knock three times on the floor’, and I knocked on the floor.”

She told police that, as he was attacking her, he said: “You just another crack [expletive] from the street; no one will know if you missing.”

Mr Jackson said that Ms Frazier was lucky to escape the alleged serial killer: “My niece would probably fit the same profile of many victims, so she is fortunate, very fortunate,” he told reporters.

Cleveland police have expanded their investigation to include three murders that took place near Mr Sowell’s previous home before he was sent to prison for 15 years for a 1989 rape. When a local news reporter visited one of Mr Sowell’s previous homes she found a bone in the narrow space underneath the raised house.

A woman in California who saw Mr Sowell on television claims that he raped her while he was stationed in the military there. Investigators are also looking again at any unsolved cases while he served with the Marines in North Carolina and Okinawa, Japan.

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