Five men killed in an explosion at an industrial unit may have been producing illegal alcohol.
Investigators have found evidence to suggest the unit in Boston, Lincolnshire, was being used as an illegal distillery.
Five men, believed to be eastern European, died after the blast last night, while a sixth suffered 75% burns and underwent surgery today.
Lincolnshire Police Superintendent Keith Owen said: "What I can confirm is that we have found chemicals on the premises which tend to indicate either the manufacture or production of alcohol."
Earlier this year police, Trading Standards and Revenue and Customs swooped on six stores in the town, seizing counterfeit vodka.
The spirit was later found to contain "Isopropyl" alcohol, widely used as a solvent and a cleaning fluid.
Last month Trading Standards bosses said Boston Borough Council's licensing committee had revoked the alcohol licence of one store and suspended that of another with action due to be taken against the other four.
Speaking at the time, Sergeant Jock Watt, from Lincolnshire Police's licensing team, said: "These decisions send out a clear signal that operating in this way will not be tolerated in Boston, or indeed across Lincolnshire.
"We hope that other premises who may have been tempted to sell smuggled or counterfeit goods from their venues will see this as a deterrent."
Mr Owen said: "It has been a problem in the past. We have obviously run an operation recently with HMRC and Trading Standards and that was a joint operation.
"Those people are still involved in this operation to help us to try and piece together what happened last night.
"This does not appear like a huge operation but again it's far too early to speculate.
"All I can tell you at the moment is in that room there are what appear to be the component parts of the manufacturer of an alcoholic drink.
"Until we have investigated I don't want to speculate on the size of the operation or even if there is an operation."
Police are trying to identify the five men - whose bodies have been removed from the unit - with post-mortem examinations due to be carried out.
Mr Owen said police did not know who they were and urged anyone with any information or who may have missing relatives to contact them.
Officers have carried out painstaking searches to work out what happened to cause the explosion.
"What we need to appreciate is that these inquiries are going to be very slow and very meticulous," Mr Owen said.
"We are working to identify those unfortunate people who died, and a main - but not exclusive - line of inquiry is the manufacture of alcoholic drinks."