Shanghai: Investigators probing a fire that ravaged a downtown Shanghai high-rise apartment and killed at least 58 people say an energy-saving project that used illegal contracts, unsafe materials and unqualified workers is mainly to blame.

Monday's blaze gutted the 28-story building, leaving 70 injured and dozens unaccounted for, and prompted a belated crackdown on illegal construction work and lax fire precautions. It also has raised alarm over widespread use of flammable insulation used to retrofit buildings to meet new energy standards.

The death toll has climbed as new victims are found in the charred rubble or those being treated die of their injuries. As of Friday morning, state media said it stood at 58, up from 53 the day before.

"The accident should not have happened and was completely avoidable," Luo Lin, head of the State Administration of Work Safety, said on his agency's website.

Luo listed a litany of problems with the government-sponsored energy-saving project: illegal use of unlicensed subcontractors, poor construction site management, lax local safety supervision and use of highly flammable nylon netting, insulation and other materials that caused the fire to spread out of control throughout almost the entire building.

Crackdown

The disaster has prompted Shanghai and other city governments to crack down on such practices. Beijing authorities ordered all renovation and energy-retrofitting projects in the city to be suspended pending inspections and "rectification" of any problems, according to a notice on the website of the Beijing Construction Committee.

Anguished family members and others angry over the government's handling of the disaster are demanding answers.

"The government owes us a reasonable explanation and serious investigation. They have already lost the chance to apologise to those who were killed," said Wang Lianguo, a neighbour who said he spotted the fire while doing laundry.

Authorities say they have identified 26 of the 58 bodies taken from the building. More than 30 people reportedly remain missing from the blaze.