Neighbours have paid tribute to the three people that died in a house fire on Stuarts Close in Hemel Hempstead on Sunday, March 29.
The alarm had been raised by neighbour Peter Downer who saw smoke coming from the bathroom at the front of the property.
Mr Downer, 67, said: “We called the fire brigade when I saw smoke coming from the toilet. We were shocked when we heard what happened.
“They were a quiet family and had lived here for a long time.”
The family have not been formally identified but have been named by neighbours.
According to the Mr Downer, Gary, 57, had worked as a draughtsman, Caroline, 50, had worked at a supermarket.
Their daughter Katie, 24, worked with animals.
The couple had another son and daughter.
Another neighbour said: “They were a lovely family. They had been here for about 30 years. It is a terrible tragedy. We don’t know what happened.”
Police and forensic officers continued to work at a house on Stuarts Close in Hemel Hempstead on Tuesday, March 31.
A murder investigation has been launched.
Detective inspector Iain MacPherson, from the Beds, Cambs and Hertfordshire Major Crime Unit, said: “Police are following all lines of enquiry and considering all possible motives.
“We are dealing with three suspicious deaths and are not looking for anyone else in connection to this incident at this time.”