UPDATE: Police have named the victims of the house fire as Claire James, 27, Josie Leighton, 32, Tyler Green, nine, and Jordan Green, 12.
Two children have died in a house blaze that also killed two adults, while a third child is in hospital for minor injuries.
The fire in North Wingfield, near Chesterfield, north Derbyshire, occurred in the early hours of Wednesday.
A Derbyshire Police spokesman said officers were conducting a joint inquiry with the fire service into the cause of the blaze, which was reported to the emergency services at 5am.
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A police spokesman said: "Two adults and two children have died as a result of the fire.
"Williamthorpe Road will be closed for several hours and local diversions are in operation."
Anyone with information which could assist the inquiry into the fire is asked to contact Derbyshire Constabulary on 101.
Firefighters from Clay Cross, Chesterfield and Staveley attended the blaze, with the first appliance arriving at the scene eight minutes after the emergency call was received.