Investigators are probing the cause of a devastating explosion that killed five men inside an industrial estate unit.

A sixth man was taken to hospital suffering from severe burns following the blast at the Broadfield Lane industrial estate in Boston, Lincolnshire, on Wednesday evening.

Teams of emergency workers were scrambled to the 30ft by 15ft unit shortly before 7.30pm after several 999 calls from members of the public.

Steve Moore, area manager from Lincolnshire Fire and Rescue Service, said a total of six fire engines were sent to the scene. "When the first crews attended they were faced with a really serious fire and a casualty who was outside the building suffering from burns," he said. "Their initial reaction was to treat the casualty. The incoming crew then started to fight the fire, it was a really hot, intense fire."

The officer said the fierce flames set alight a car outside the unit and also buckled its roller shutters, meaning crews were forced to use hydraulic equipment to cut their way into the block. "At that point we received further information that there may be further casualties," he added

Mr Moore described the incident as one of the most serious he had ever seen in his 28-year career. "As far as the crews I have spoken to, its the single greatest loss of life in fire in their experience," he said.

A Lincolnshire Police spokeswoman confirmed that five men had been killed in the blast. The sixth man was taken to Boston Pilgrim Hospital, suffering from serious injuries, before being transferred to the Queen's Medical Centre, Nottingham, she added.

"Inquiries are ongoing and will be ongoing throughout the night to establish the cause of this explosion," the spokeswoman said.

Ian Nuttall, 42, who lives 200 yards from the scene, said he noticed a commotion and smoke coming from the unit at about 7.30pm. He described it as one of four "lock-ups" that can be rented out to people, with another four opposite it. He said he did not know anyone who used it, or what they used it for. "There was a rumour going round that it was some Polish nationals who have been brewing their own vodka which is a bit of a problem around here at the moment," he said.

Police would not confirm reports that the explosion occurred because of illegal alcohol brewing, but said investigators were keeping an "open mind and following up all relevant lines of inquiry."