Two young girls, aged around 7 and 11, were discovered with a man, 45, and a woman, 36, at the address in Costessey, near Norwich, at around 7am on Friday.
The man was named locally as Barlomiej Kuczynski, who lived in the house with his wife Nanthaka. It has been reported that the two girls who died were his daughters - although police have yet to formally identify the bodies.
The bodies were found after a call from a member of the public shortly before 7am on Friday.
However, it has now emerged that the force failed to respond to a previous call from a man at the address at 6am, an hour earlier.
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 same address last month.
A force spokesperson said: “A second referral has been made to the IOPC today (20 January) following the identification of a 999 call made yesterday morning at 6am by a man at the address and police resources were not deployed.”
It is understood that all four found dead were from the same family. Three lived at the address and the fourth was there "non permanently".
The community has been in shock and mourning after the news.
Norfolk Police said uniformed officers would be on the Queen’s Hill estate throughout the day, a police cordon remains in place and forensic investigations will continue inside the property.
Meanwhile, detectives have been carrying out house to house enquiries, speaking with witnesses and examining local CCTV footage.
Detective Chief Inspector Chris Burgess, from the Norfolk and Suffolk major investigation team, said: “We’ve had a heavy police presence in the area since yesterday morning and there’s understandable concern in the local community.
“However, their help and support in the investigation has been unwavering and on behalf of everyone involved in this devastating incident, we’re extremely grateful for that.
“Today, the focus of our inquiries remains at the address and we’re examining local CCTV. While we’re still piecing together what’s happened, at this stage we remain satisfied that this is an isolated incident.”
He said all four people were found with injuries and post-mortem examinations would be held to establish the cause of death.
“We’re aware of commentary on social media and in news media, however, I would emphasise that formal identification is yet to take place,” Mr Burgess said.
“As I said yesterday, we believe the man and two children lived at the address, and while the woman was staying there, she wasn’t a permanent resident."