A two-year-old girl has died after a fire at a caravan park in Ingoldmells, Lincolnshire Police has said.
Officers said they were called to reports of a fire at about 10.30pm on Monday at Sealands Caravan Park near Skegness, where a caravan was alight.
A woman and three of her children were able to escape the vehicle safely, but her youngest child, the toddler, died.
Police are treating the cause of the blaze as "unexplained".
Lincolnshire Fire and Rescue said that when their five crews arrived on the scene, the blaze was "already well-established and aggressive firefighting was needed to extinguish it".
The survivors were taken to hospital for medical treatment and have since been released.
About 50 people were asked to leave caravans close to the blaze and were provided with emergency accommodation at the Laver Leisure site.
Detective Inspector Jo Fortune, senior investigating officer, said the circumstances which led to the fire are still unclear.
"This is a devastating incident for all involved," she said.
Officers said they are working closely with specialist teams to understand what happened and an investigation team will be at the scene throughout the day.
Chief superintendent Kieran English said: "At this point of time it is unexplained, but hopefully as the day progresses we may have some indication in terms of the causation of the fire."
"I've got children. This is absolutely tragic. My thoughts and my prayers go to the family and their friends at this really sad time," the officer added.
People who were at the caravan park last night have been urged to speak to police if they have not done so already.
Witnesses have been asked to send officers any video footage they may have taken.
"This is particularly harrowing, with a family losing a child, and we'd ask that people remember those victims and not share footage online," DI Fortune added.
After investigations are complete, Lincolnshire Fire and Rescue said local fire crews and their community safety team will be "on hand" to talk to people in the area and address any fire safety concerns.
"Our thoughts and deepest condolences are with the family at this time," said Matt King, Divisional Commander for the East Division at Lincolnshire Fire and Rescue.
Ch Supt English said: "We've a long way to go before we can ascertain the facts in this tragic incident.
"But Lincolnshire Police and Lincolnshire Fire and Rescue are determined to find answers for the family."
Watch the latest videos from Yahoo News UK