Chemicals found at an industrial unit in Lincolnshire where an explosion and fire killed five men indicate alcohol was being made there, police have said.
Emergency services were called to the Broadfield Lane Industrial Estate in Boston at about 1900 BST on Wednesday.
One man who survived is having surgery after suffering 75% burns. Police said an unidentified spirit was probably being produced illegally at the site.
Supt Keith Owen said the exact cause of the fire was still being investigated.
"It is a smoke-damaged area," he said. "We are working very closely with the fire service because they are the people who can identify what the component parts are.
"They have got experts in there, we have got forensic experts in there, and I wouldn't like to speculate on exactly what sort of alcoholic drinks we are talking about."
Describing the deaths as "a tragedy", police said they intended to interview the injured man as soon as possible to try to identify the dead and find out how the fire started.
The bodies have been removed from the building for post-mortem examinations.
It is believed the men had died instantly in the force of the explosion. The fire was so intense the metal door of the unit was buckled and cars parked nearby were damaged.
The industrial estate, which is close to the town centre, is made up of between 12 and 15 small units.
Earlier this year, goods were seized - including fake vodka - from six international stores in the town during raids by HM Revenue and Customs [HMRC], police and Lincolnshire Trading Standards.
Tests of the counterfeit alcohol, seized in March, showed it was found to contain chemicals often unsafe for public consumption.
Mr Owen said the scene appeared to show a "small-scale operation" but he could not speculate on the details of it.
"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.
"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."
A spokesman for HMRC said: "Yesterday's tragic events in Boston have underlined the risks that go with the illegal distillation of alcohol.
"In just over the last 12 months HMRC, working with other law enforcement agencies, has closed down three illegal stills and six men have been prosecuted for producing counterfeit vodka, resulting in prison sentences totalling over 56 years.
"Illegal alcohol undermines all honest alcohol traders whilst putting at risk the lives of those who consume and produce it."