Search teams are combing woodland where the naked bodies of two women were found by police already hunting the killer of three prostitutes.
Annette Nicholls, 29, was reported missing by her family
Suffolk Police said it is likely the bodies found near Ipswich on Tuesday are those of two missing prostitutes.
Paula Clennell, 24, has not been seen since Saturday, while Annette Nicholls, 29, has been missing since 4 December.
Police have already linked the murders of the three women whose bodies were found near Ipswich within 10 days.
Det Ch Supt Stewart Gull, who is leading the inquiry, said it was conceivable the women knew their killers.
"It might be a regular client, a regular punter, and I think that potentially the working girls of Ipswich, maybe unwittingly, hold the key to who is responsible for the deaths of Tania, Gemma and Anneli, who was found on Sunday," he said.
"We know that they have been murdered, and possibly now Paula and Annette, although I stress their identity is yet to be confirmed."
The first body discovered on Tuesday in Levington was found by a member of the public and the second was spotted nearby by a police helicopter.
The site where they were found is off the main A14 trunk road between Ipswich and Felixstowe docks close to a railway line, the Orwell estuary and a marina.
The area is close to where the body of Anneli Alderton, who had moved to the area from Huddersfield in West Yorkshire, was found on Sunday. The bodies of Gemma Adams, and Tania Nicol, were also found nearby.
Paula Clennell's father, Brian, told the BBC's Today programme that he was not aware his daughter was working as a prostitute and he pleaded for anyone with information to contact police.
"The only thing that I'm getting now is that two bodies have been found and it could be my daughter. I never knew that she lived the life that she did," he said.
"Somebody out there must know, somebody that's doing this. He's sick, he's got to be caught. It could be somebody's father, it could be somebody's uncle, it could be anybody.
"Anybody with information just come forward and my thoughts go out to the families of the three that's confirmed."
Paula Clennell has not been seen since Saturday
Miss Clennell gave an interview to ITV on 5 December in which she said she was prepared to go back on the streets despite the emerging danger because "I need the money".
But she admitted the killings had made her "a bit wary about getting into cars".
The first woman found on 2 December was Gemma Adams, 25, naked in woodland at Hintlesham, on the outskirts of Ipswich. She had last been seen on 15 November.
On 8 December the body of Tania Nicol, 19, was found in nearby Copdock. She was the first to go missing and had last been seen on 30 October.
The naked body of the third prostitute, Anneli Alderton, 24, from Colchester in Essex, was discovered at the weekend in Nacton, a few miles further east.
Mr Gull said: "This is so fast-moving, we need to take stock and maximise opportunities to recover forensic evidence from the scenes before formally establishing whether they are linked or not.
"We need to catch this person or persons as quickly as possible."
Mr Gull said no further prostitutes had been reported as missing in Ipswich and about 200 officers were involved in the search for the killer.
He added: "We have had a tremendous response from the public. Over 450 calls yesterday and I suspect a similar amount today."
Labour MP for Ipswich Chris Mole said: "I think people are very nervous and very worried because this is 'unprecedented' not just in Ipswich terms but in national terms.
"Nothing of this pace in terms of the numbers of the bodies being found, five in 10 days, has been seen anywhere else in the UK ever.
"I think that understandably worries people that they don't know what's going to happen next."
Church leaders from across Suffolk said prayers will be said at services this weekend for the prostitutes and their families.