A 40-year-old man is being questioned by police on suspicion of murdering three women sex workers in Bradford after body parts were found in a river.
Stephen Griffiths was arrested on suspicion of killing Suzanne Blamires, 36, who was last seen on Friday.
He is also suspected of killing Shelley Armitage, 31, and Susan Rushworth, 43.
Mr Griffiths is understood to be a Phd student and is believed to be studying criminology. Police can continue questioning him until Thursday evening.
The BBC understands remains found in the River Aire in Shipley on Tuesday are those of Ms Blamires, although they have not been formally identified.
Ms Armitage, from Allerton, Bradford, has been missing since 26 April and Ms Rushworth, from the Manningham area, has not been seen since June 2009.
Police are also investigating possible links to the case of Rebecca Hall, 19, who worked as a prostitute in the city and was killed in 2001.
Her body was found in the Allerton area of the city, near to where Ms Blamires and Ms Armitage lived.
Assistant Chief Constable Jawaid Akhtar said the remains found on Tuesday had not been identified, but belonged to one person.
He said detectives had obtained a warrant of further detention to question the 40-year-old man until Thursday evening.
ACC Akhtar said: "This is a very thorough and painstaking inquiry into three missing people who are sex workers, with all the necessary resources and expertise devoted to it.
"The families of Suzanne, Shelley and Susan are all being supported by our family liaison officers as the inquiry progresses."
It is understood that CCTV footage is playing a major part in the investigation by West Yorkshire Police who started a poster appeal earlier this month to try to trace Ms Armitage - last seen in Rebecca Street in Bradford city centre.
At the time detectives described her as "a much-loved daughter and sister" and said her family were growing increasingly concerned for her welfare.
Ms Rushworth, a mother-of-three who is known as Sue or Susie, was last seen near to her flat at Oak Villas, Manningham.
At the time of her disappearance police said she suffered from epilepsy, had never been missing before and had been getting help for her heroin addiction.
Ms Rushworth's son James, 23, appealed for information, saying: "We are all very worried about her.
"We're a close family and we're not coping very well with her disappearance.
"There is no reason that she would have just left. She's only recently started seeing her grandchildren and was getting to know them."