A woman found dead at her home is believed to have been drowned in the bath by somebody she knew, police said.
The body of Polish bakery worker Agnieszka Dziegielewska, 30, was discovered in the bathroom of her home on Horsefair Close, Swinton, in South Yorkshire, last Thursday.
Det Supt Colin Fisher said: "I think it will probably turn out to be death by drowning and I am confident that she knew her killer.
"I believe the deceased let the killer or killers into her home.
"Her killer left after the attack, locking the door in the process."
A 31-year-old man from Doncaster arrested on suspicion of murder remained in custody today.
Det Supt Fisher added: "The post-mortem investigation carried out on Friday January 29 requires additional information before a cause of death can be formally established. However, I believe she was killed."
Ms Dziegielewska, who moved to the UK four years ago from Bialystok in north-east Poland, was last seen leaving the Maple Leaf Bakery at around 6pm on Wednesday January 27.
Her body was found after she did not turn up to work the following day and police were alerted.
Police are now trying to trace a red VW Golf with the registration number W991 OSP, which is believed to be missing.