Five men have been killed and a sixth has been seriously injured in an explosion at an industrial estate in Lincolnshire.
Police, fire and ambulance crews were called to the Broadfield Lane Industrial Estate in Boston at about 1900 BST on Wednesday.
A Lincolnshire Police spokeswoman said she believed the men died instantly in the force of the explosion.
Police are investigating claims the men may have been brewing illegal alcohol.
A spokesman for the force appealed for anyone with information about the men and what activity was taking place at the unit to contact officers.
The sixth man was taken to Boston's Pilgrim Hospital but later transferred to the Queen's Medical Centre (QMC) in Nottingham.
Nerys McGarry, from Lincolnshire Police, said it was not yet clear what had caused the blast.
The five men were killed instantly in the explosion "We do not have any further information about the men, their ages and where they are from but we will be making inquiries throughout the night and can give a further update in the morning," she said.
BBC Lincolnshire reporter Scott Dalton, who was at the scene, said residents in the area had seen thick, black smoke coming from the industrial estate.
"Locals have been telling me they didn't even hear an explosion or even a bang," he said.