Police investigating the deaths of three prostitutes have said they are concerned for two other missing women.
The naked bodies of Gemma Adams, Tania Nicol and a third woman have been found near Ipswich in the past eight days.
Suffolk Police are searching for a fourth prostitute Paula Clennell, 24, and a fifth woman, Annette Nicholls, also a prostitute.
Assistant Chief Constable Jacqui Cheer urged women, particularly in the party season, not to go out at night alone.
Ms Nicholls was reported missing by her family and was last seen on either 3 or 4 December.
Police said Paula Clennell had spoken to a friend but they are still "concerned" about her welfare.
Earlier, in a direct appeal to prostitutes, ACC Cheer said: "Please stay off the streets, if you are out alone at night you are putting yourself in danger.
She added: "We are coming up to the party season and up to Christmas.
"There will be groups of women going out and I would say you have really got to look after each other, plan how you are going to get there and come home together.
"Whatever happens on your night out, do not leave your friends alone and make sure you get home safely."
Detectives have said there was nothing to link the inquiry with the discovery of a woman's body in a river in Lincolnshire on Saturday.
Ms Adams, 25, and Ms Nicol, 19, worked together and went missing from the red light area of Ipswich.
Ms Adams vanished on 15 November and her body was found in a stream at the village of Hintlesham, Suffolk, on 2 December.
Ms Nicol disappeared on 30 October and her body was discovered on Friday in the same stream at Copdock, near Ipswich.
A prostitute interviewed on BBC News 24, who gave her name as Kelly, said she knew Tania Nicol.
"She was very into martial arts, that I do remember. She was a very nice girl. She seemed very healthy and looked after herself," she said.
Det Ch Supt Stewart Gull said: "While we can't formally link the discovery of the body at Nacton with the two murders, the facts speak for themselves.
"I do not know who we are looking for. He may be local, he may be from away. We could draw a number of conclusions as to where the bodies have been deposited and found. Anything is possible."
Det Ch Supt Gull said Ms Clennell, who was last seen on Saturday, had been reported missing by a friend.
"We know that Ms Clennell uses a number of addresses in Ipswich and we are currently checking these to establish her whereabouts.
"We would urge Paula or anyone who knows of her whereabouts to call us immediately so that we can be reassured that she is safe and well."
Gemma Adams: Went missing on 15 November, body found by a stream near Hintlesham on 2 December
Tania Nicol: Disappeared on 30 October, body discovered 8 December in Copdock
Third body discovered on 10 December near Nacton