A man and woman found at a house with two young girls in Norfolk both died from stab wounds to the neck, a post-mortem examination has revealed.
The bodies of four members of the same family were discovered at an address in Costessey, near Norwich, on Friday morning.
A man called 999 from the property on Allan Bedford Crescent at around 6am that day, but police were not dispatched there.
Officers made the discovery about an hour and 15 minutes later after a member of the public alerted them at around 7am.
Norfolk Constabulary, which has referred itself to the police watchdog over the delay, is not looking for anyone else in connection with the tragedy.
Post-mortem examinations carried out on Sunday found both the 45-year-old man and woman, 36, died as a result of stab wounds to the neck.
The bodies of the two girls will be examined on Wednesday.
The force had already referred itself to the Independent Office for Police Conduct on Friday over police contact about a missing person inquiry at the address last month.
Detectives said the man and two children lived at the address, but the woman was visiting and lived elsewhere. All four were found with injuries.
The man has been named in reports as Bartlomiej Kuczynski.