Bartolmiej Kuczynski, 45, Kanticha Sukpengpanao, 36, Jasmin Kuczynska, 12, and Natasha Kuczynska, nine, were found after a member of the public raised concerns for their welfare.

An emergency 999 call was made at around 6am by a man from the Norfolk address where the four people were found, but police failed to respond on Friday, it emerged at the weekend.

During the phone call, the man expressed concerns for his own mental state, saying he was confused, but was advised by police to seek medical advice, the Independent Office for Police Conduct (IOPC) watchdog said on Tuesday.

Officers discovered the bodies, including a father and two young girls, believed to be his daughters, more than an hour after the emergency call, at around 7.15am, after forcing their way into the property in Allan Bedford Crescent, Costessey, near Norwich.

They had been alerted by a member of the public, who was concerned for the welfare of the people inside, shortly before 7am.

Post-mortem examinations carried out on Sunday found the woman died as a result of stab wounds to the neck while the man died as a result of a stab wound to the neck.

All four of the individuals were found with injuries.

Post-mortem examinations for the two girls will be carried out tomorrow, police said.

Detectives confirmed on Sunday they were not looking for anyone else in connection with the incident.

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Nina Crisan, whose son knew one of the girls, Jasmin, described her as a "very, very sweet girl".

"She had very calm and cool energy, as my son would say," she told Sky News on the weekend. "She was just a lovely, lovely, lovely kid."

She said the incident had come as an "absolute shock" to those who lived in the area.

She added: "This is a really close community. And we all, even if we don't know each other directly, sort of know each other through the children, or through dog walking."

Norfolk Police has referred itself to the IOPC in relation to the 6am call, "to which police resources were not deployed".

Providing details on the phone call, Charmaine Arbouin, IOPC regional director, said: "Norfolk Constabulary established that the man had made a 999 call to the force shortly before 6am on 19 January.

"During that call the man expressed concerns for his own mental state saying he was confused.

"He was advised to seek medical advice and police did not attend.

"At around 7am the force received a call from a dog walker concerned for the welfare of those within the home.

"Officers attended shortly after and, tragically, found the man, a woman and two children dead."

Norfolk Police also said it will investigate and will be examining if the contact its officers had with the man was "appropriate and in line with force policy, training and procedures".

The force had already contacted the IOPC over the incident because officers attended the property on 14 December last year in relation to a missing person inquiry.