Two adults and two children were found dead at a house in Newcastle upon Tyne today.
The grim discovery was made just before 9am.
Northumbria Police said they went to a house in Hawthorn Gardens, in the Kenton area of the city "acting on information received".
A spokesman said the two adults and two children were believed to be members of the same family. Their deaths are being treated as suspicious.
He said police were urgently trying to trace a man that visited the address where the bodies were found.
Neighbours of the family in the leafy residential suburb spoke of their shock today after hearing about the deaths.
One neighbour said they were unaware of anything untoward at the house until police arrived in the area.
Northumbria Police sealed off the quiet street, which consists of 1930s style semi-detached housing, while investigations continue into what happened.
Elizabeth Cessford whose garden backs onto the family's home, said they were a lovely family and it was as tragedy.
"I used to see them in the garden, which was just full of toys," she said. "I used to see the children playing in the garden and they were laughing and enjoying themselves.
"They just looked like a happy family. I'm absolutely devastated, I'm really shocked. This is such a quiet street, it's a very nice area and the sort of place you say 'hello' when you pass people in the street."
Mrs Cessford, who lives in Mountfield Gardens, went on: "I would see the children playing on the trampoline jumping up and down and having a really good time. I would think they were really happy children.
"I didn't really know the family, but I'm absolutely shocked by what has happened."
Mrs Cessford said she would often say hello to the family if she saw them in the street.
"They seemed just a normal family and we didn't really see anything until we came back from the shops and we saw that the top of the road was closed and we just wondered what was going on.
"I thought it could have been a gas leak or a bomb scare."
Another neighbour in Mountfield Gardens, Claire Spires, said she didn't know the family, but was shocked such a tragic incident could happen in such a nice area.
"I didn't see anything this morning and the first time I realised there was a problem was about 9.30am.
"We've never had any problems living here. I am shocked that anything like this could have happened so close."