Raging flames were seen bellowing out from the Tabmaster UK Ltd building, in Waterworks Road, Coalville, shortly before 10am, on Friday.
Six fire engines were needed to tackle the blaze, which has left the premises severely damaged.
Police were called to close off parts of Waterworks Road, Cropston Road and Beechtree Road.
Watch manager at Coalville fire station Martin Ballard said the roof was not currently a danger to members of the public.
He said: "The unit has asbestos sheeting in the roof but it wasn't the roof that was on fire.
"It was a severe fire, we had crews from Ashby and Shepshed here shortly after we arrived."
Mr Ballard said the cause was still under investigation and that the unit was unoccupied at the time of fire.