All five victims of one of Britain’s most prolific serial killers were suffocated or strangled and left naked but for their jewellery, senior detectives have told The Times.

Police sources said that as a result of the “striking similarities” uncovered they had been able to rule out any link between previous unsolved murders or attacks by strangers across the country in recent years. Last night items of women’s clothing were found in the River Orwell, which runs close to Nacton and Levington where three of the bodies were found.

Today the first of 100 specialist detectives from across the country will arrive in Ipswich to double the size of the investigative team by the weekend.

Serial killers frequently leave a “trademark” signature — following a particular pattern of behaviour in the way they leave their victims. Leads police are pursuing include:

• That the killer could be a visitor to the area or working temporarily in Suffolk;
  
  
• The killer, or killers, seem to have a good grasp of forensic science — dumping two of the victims in water, which can destroy DNA evidence, and stripping them of their clothes;
  
  
• That he is more familiar with the area where he left the first two bodies, which is to the west of Ipswich, than the sites where the three later bodies were found, to the east along the A14;
  
  
• A claim from a prostitute that the killer could be a “chubby man” driving a blue BMW. A friend of the third victim to be found, Anneli Alderton, told officers that she saw the man driving away with Ms Alderton beside him.
  
  
  
  The inquiry hotline has receivedmore than 4,000 calls from the public in two days. Police forces across eastern England have been asked to pass any female clothing they find to the Suffolk inquiry.
  
  Officers are also tracking CCTV footage along the A14, which links the locations of all the bodies and runs close to the town’s red-light area. But they are concerned that the attacker may strike elsewhere before he is caught.
  
  Norfolk police have increased patrols in the Norwich red-light area and have urged prostitutes to keep in contact with local outreach workers. Cambridgeshire police told sex workers to be “extra vigilant, and report suspicious or unusual activity by clients”.
  
  Last night police were playing down reports of a possible link between the Ipswich deaths and the murder of a young woman in Norwich in 1992 murder. Natalie Pearman, 16, was found strangled in the Ringland Hills area after disappearing from the city’s red-light district. Norfolk police this week paid a visit to members of the victim’s family but Suffolk police said this was purely routine.
  
  Other reports this morning claim that a text message sent from Paula Clennell’s mobile phone to a concerned friend on the day she disappeared may have been sent from the murderer to buy time.
  
  Detective Chief Superintendent Stewart Gull, who is heading the inquiry, said there were still significant challenges facing them. “These tragic events have clearly overwhelmed us in terms of our capability and capacity,” he said.
  
  He said that his force had begun high-visibility patrols in the Ipswich red-light area since Ms Nicol went missing on October 30. Despite that, four other women had been taken from the streets and murdered.
  
  Mr Gull defended his force’s record during what he called “a crime in action”. He added: “A number of prostitutes operate off-street, it may be they arranged to meet that person by phone.” Post mortems are likely to confirm the similar cause of death of all five victims.
  
  Downing Street officials called the Chief Constable of Suffolk on Tuesday on Tony Blair’s orders to ensure that he had the resources he needed. He had replied that he did.
  
  The Prime Minister told the Commons: “There may well be lessons that we have to learn as a result of the terrible events of the past few weeks but I think those lessons are best learnt in a considered, not a reflex way.”

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