Members of a 500-strong task force hunting a suspected serial killer canvassed motorists and pedestrians passing through a red-light district to try to trace the final steps of five murdered prostitutes in an eastern England town, police said Sunday.

More than 400 people in Ipswich were stopped and questioned, Detective Chief Superintendent Stewart Gull said. In particular, they were asked if they had seen one woman, 24-year-old Paula Clennell, whose naked body was discovered at the side of a busy road last Tuesday.

A frightened Clennell was still working the streets — to satisfy her drug cravings, she told a television crew five days before she disappeared — after the bodies of three other sex workers were discovered. She was last seen in the early hours of Dec. 10.

On Dec. 12, her body was discovered, and police have said she died as a result of "compression to the neck."

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Gull said that 340 specialist investigators from forces across Britain had joined 160 officers on the task force. By Sunday morning, police had received more than 10,000 calls from the public.

Interpol has offered assistance, and Gull said it would be considered and accepted "if necessary."

On Saturday, police released closed-circuit television footage of Anneli Alderton, another 24-year-old prostitute whose body was discovered Dec. 10, hours before Clennell disappeared. Police said she had been strangled.

Alderton — who was three months pregnant at the time of her murder — was last seen Dec. 3, the evening the footage was captured aboard a train south of the city.

Calls prompted by the release of the images allowed detectives to determine that Alderton had ended up in Ipswich, but "we still need to know where she was after Dec. 3," Gull told reporters.

And he said that the team probing the killings were still unable to determine the final movements of another woman, 29-year-old Annette Nicholls. She was last seen alive on Dec. 5 in Ipswich's red-light district.

Detectives have only been able how to determine how two of the five women were killed. Post-mortem examinations on the other three women — Nicholls, 25-year-old Gemma Adams, found Dec. 2, and 19-year-old Tania Nichol, discovered Dec. 8 — were inconclusive.

"We haven't got a murder scene at this stage, and once we establish that we'll start to complete the picture. I'm still waiting on a cause of death for three of these young women, and once we've got those results it may indicate if we're looking for a weapon," Gull told reporters. "We're keeping an open mind as to whether any form of weapon was involved."

Gull also said that a man who had tried to abduct a woman in Ipswich about a month ago has not been spoken to by detectives investigating this case.

"Nobody has been eliminated at this stage. We know who that individual is. He has been released on bail," Gull said. "We will take further action if we think it is appropriate."