The fire which engulfed the former Toys R Us store in Peterborough was started accidentally, according to the county’s fire service.
Eight fire crews battled through the early hours of the morning to put out the blaze, with the last firefighter only leaving the scene at around 5am, five hours after the fire was first reported.
Police closed Bourges Boulevard between Westfield Road and Mayor’s Walk as firefighters from both Cambridgeshire and Lincolnshire tackled the blaze.
The road reopened at around 5am.
Crews from Dogsthorpe, Stanground, Thorney, Whittlesey, Yaxley, Sawtry, Huntingdon and Ramsey, as well as the Peterborough Volunteer Fire Brigade, attended the scene, along with crews from Crowland, Market Deeping and Boston in Lincolnshire.
The firefighters saw the flames going through the roof with the fire significantly damaging the building, causing the front of the building to collapse.
A Cambridgeshire Fire and Rescue Service spokeswoman said this morning the cause of the fire had yet to be determined, but following an investigation it has been judged to have started accidentally
A spokeswoman said there was nothing on site to suggest the fire had been started deliberately, but the exact cause has not been pinpointed.
There have been no reports of any injuries.
The store closed last year after Toys R Us went into administration.
Photos taken this morning showed the damage caused to the former store.