Flowers have been placed outside the home in Ruislip, northwest London, where a woman and two children were found dead.
It is understood that police are not looking for anyone else in connection with the deaths of three people at a house in north-west London.
Ambulance services confirmed that a woman and two children were found dead at the scene.
A spokeswoman for London Ambulance Service said: "We were called at 6.40pm to reports of an incident in Midcroft, Ruislip. We sent three ambulance crews, two single responders in a car, two officers and our hazardous area response team.
"Sadly three patients, a woman and two children, were dead at the scene."
A woman and two children have been found dead at a house, police said.
The 34-year-old woman and two girls, aged nine and four, were discovered at a property in Midcroft, Ruislip, at 6.40pm last night.
Scotland Yard said that detectives from the Homicide and Serious Crime Command were investigating.
At this stage, the deaths are being treated as unexplained and next of kin have been informed.