MADRID, Feb 13 (Reuters) - The biggest fire in Madrid’s history gutted a 32-storey skyscraper in the Spanish capital’s financial district on Sunday without causing injuries but raising fears the charred tower could collapse.

As scores of firefighters quelled the final flames inside the Windsor building almost a day after it caught alight, authorities said the spectacular blaze was probably started by an electrical short-circuit.

Officials said there was still a risk that Madrid’s eighth tallest building-now reduced to a blackened concrete skeleton — could disintegrate as its structure cooled.

"It is clear the structure has been damaged and has suffered high temperatures, and we cannot be certain that a pillar, girder or some other structural element will not collapse," Javier Sanz, fire chief for the Madrid region, told state radio.

At its peak, the fire lit up the Madrid sky like a huge torch. Flames devoured the 106-metre-high building from the top down, raining burning debris on to the street below. Surrounding buildings were evacuated and roads blocked.

Seven firefighters were treated for smoke inhalation.

"We have confronted the most extensive fire that this city

has ever had," Madrid Mayor Alberto Ruiz Gallardon said.

Spanish media on Sunday questioned how the blaze was able to devour the building without triggering fire alarms.

The building, which was one of Madrid’s first skyscrapers, completed in 1979, had been undergoing building work on its upper levels. State radio said the privately-owned building had been insured for a sale value of 83 million euros in 2003.

U.S. accounting firm Deloitte & Touche, which has its offices in the building, said it would attend clients normally on Monday and reroute calls to other bureaux in Spain.

Streets, shops and offices in the area and some sections of the Metro network will remain closed until officials are sure the building is safe, Mayor Ruiz Gallardon said.

Prime Minister Jose Luis Rodriguez Zapatero visited the scene and offered the government’s support to local authorities "so that we can overcome this situation as soon as possible and life in this area can get back to normal".

The blazing tower evoked memories for many Spaniards of the Sept. 11, 2001, attack on the World Trade Center in New York.