The bodies of a man and two young children have been found next to a car on a bridleway.
Hampshire Police were alerted at 6.15pm on Sunday by a member of the public who discovered the bodies in Newton Stacey, Andover.
They are thought to be Michael Pedersen, 51, of Chertsey, Surrey, and Ben Pedersen, seven, and Freya Pedersen, six, both of Ashford, Middlesex, said a spokesman.
No-one else is being sought in connection with the deaths, police said. The coroner has been told and post-mortems will take place later.
We are currently investigating the circumstances surrounding this terrible incident and are working to establish what has led to these tragic deaths.
We are treating this as an isolated incident and we do not believe anyone else was involved.
The families of Michael, Ben and Freya have been informed and specialist family liaison officers from Hampshire Constabulary, and officers from Surrey Police, are working with them to provide support and keep them updated as the investigation progresses.
More top news
Pictures of today's events unfolding following a major security incident at the Houses of Parliament.
At least two people have died after a knifeman brought terror to the heart of Westminster.
The Cobra committee brings together government ministers with senior officials of the emergency services and security agencies.