Two young girls, a man and a woman all from the same family were found dead at a property near Norwich, police have said.
Formal identification is still to take place, Detective Chief Inspector Chris Burgess of Norfolk Police said, but confirmed that the man was 45 and the woman was 36.
Officers forced their way into an address in Allan Bedford Crescent, Costessey, shortly before 7am on Friday following a call from a member of the public.
The bodies of the four people were found inside.
Mr Burgess said: “We do believe they were all family members at this time.
“Three of the people are believed to reside at the address and another one not permanently.”
Mr Burgess continued: “I would be reassured that we’re doing a thorough investigation into this.
“I’m confident this is an isolated incident but, as I say, it’s very early on, I’m keeping an open mind.
“I would stress to the community, let’s be very aware of what we share on social media without confirmed information.
“We don’t want to cause any undue distress or give false information that might actually hamper the investigation rather than support it.”
In an earlier statement, Mr Burgess, from the Norfolk and Suffolk major investigation team, described the incident as “very distressing and tragic”.
He said he understood that news of the incident was shocking and the force would release more information as soon as they could.
A cordon is in place and detectives from Norfolk and Suffolk police forces are leading the investigation.