A woman found dead after a house fire was strangled by an intruder, police said.
Lisa Skidmore, 37, was found at the burning house in Bilson, Wolverhampton on Thursday, along with her injured 80-year-old mother.
West Midlands Police said on Sunday that a murder inquiry was under way after a post mortem examination revealed that Miss Skidmore had been asphyxiated.
The older woman was beaten unconscious by the man in the morning attack in Mill Croft and was taken to hospital with severe facial injuries, detectives revealed.
Detective Superintendent Mark Payne said: "This is a very complex inquiry and it has taken us some time to establish what has happened at the address.
"We believe that the offender assaulted Miss Skidmore before setting fire to the bedroom. He was then disturbed by (her) mother and assaulted her before making his escape.
"We have a team of detectives working around the clock to trace the person responsible so I would urge anyone who saw someone acting suspiciously around the property on Thursday morning to contact us urgently on 101."
Detectives said the man they are searching for is black, aged in his 20s, 5ft 6ins tall with a medium build and "afro" hair.
He was wearing a dark long-sleeved jacket, dark trousers and black thick leather gloves.