Staff at China Central Television (CCTV) started the tragic blaze that engulfed their $714 million headquarters on Monday night, Beijing fire authorities concluded yesterday.

The Beijing fire control bureau said CCTV officials illegally hired a fireworks squad to shoot hundreds of huge fireworks above the new construction site.

They had even set up four camcorders to record the grand display against the backdrop of the architectural wonder of Beijing's central business district.

But the spectacle turned to disaster when the fireworks were aimed at the roof of the 30-storey cultural center, the annex building north of the controversial tower dubbed the Dakucha, or the big underpants, by local residents because of its shape.

Monday night's fire, which burned for almost six hours, ended in the death of one firefighter, left seven more in intensive care at a nearby hospital and destroyed billions of yuan in broadcast facilities.

Zhang Jianyong, 29, who had been leading a fire rescue search team in the building, died from suffocation.

Zhang Hao, who was also in that team and is now in hospital, said the heavy smoke inside made it impossible for them to get out.

As of yesterday morning, the west, south and east decoration walls of the building were completely burned out, with passers-by snapping pictures of the blackened tower, which houses a luxury hotel, a television studio and an electronic data processing center.

The total cost of the disaster has not been calculated, the fire department said, but the environmental bureau in the capital recorded a maximum grade for air pollution due to Monday's fireworks spectacle.

"Setting off fireworks at oneself is totally suicidal," said 49-year-old She Dalin, a Beijing resident, shaking his head.

"We found the fireworks and the equipment were identical to those used in the Olympic Games," Luo Yuan, deputy chief of the Beijing fire control bureau, who also oversaw fire safety at the famous Bird's Nest during the Games last August.

However, one Olympic contractor for the official fireworks told China Daily yesterday that the CCTV fire had "completely nothing to do with the company".

Luo explained fireworks of this magnitude need government approval before being set off.

Policemen on patrol interfered when the fireworks were set off, but CCTV officials ignored the warnings, said Luo, adding his department have on-site videos and remnants of the fireworks as evidence.

In a live broadcast yesterday, CCTV apologized for the horrible impact of the blaze, which drew hundreds of onlookers.

"CCTV feels sorry for the great loss inflicted on national assets. CCTV sincerely apologizes for the traffic congestion and inconvenience to residents nearby," the network said.