A fire engulfed a Shanghai high-rise building yesterday, killing 42 people, as panicked residents stumbled over each other as they fled and thick smoke spread over China’s commercial hub.

The 28-storey building in one of the most densely populated districts of the city of nearly 20 million people was under renovation when the blaze broke out after lunchtime.

Bright orange flames could be seen enveloping scaffolding and spreading to the building as the fire raged, gutting much of the structure. The smoke could be seen from several kilometres away.

Photos released by state media showed residents clinging to the scaffolding, trying to escape the flames, while other images showed a helicopter lowering a rescuer down to the roof.

At least 42 people died, the official Xinhua news agency said, citing a statement from the municipal government. It said the total number of injured was unknown, but 90 had been admitted to hospital.

Authorities were investigating the cause of the accident, the statement said.

Survivor Li Xiuyun, 61, said she fled down the steps of the building with her husband, son and granddaughter from their home on the 16th floor until they met firefighters who took them to safety.

“The smoke was very strong and the glass from the windows was scalding,” she said at the Jingan District Hospital, adding that she cut her feet on shattered glass as she fled.

“My son took off his socks and soaked them with water, and we used them to cover our noses. I stumbled on people on the floor when walking.”

The building was an apartment block for teachers, according to Xinhua. Reports said most of them had already retired.

State television footage showed people, their faces smudged by soot, stumbling out of the building grimacing in pain, with rescue services helping them.

A resident identified only by her surname, Zhang, told Xinhua she lived on the top floor, and escaped down the fire exit stairs along with a dozen neighbours.

A worker surnamed Qian said she was laying thermal insulation on the 28th floor and she also ran down hundreds of steps.

“At first, I saw smoke belching out of the window and soon the room was engulfed by smoke too,” she told Xinhua.

Firefighters eventually extinguished the blaze after four and a half hours and torch beams could be seen in the darkness afterwards as rescuers searched the building’s upper levels.

A total of 156 families lived in the building, municipal officials said in a statement.

The Jingan District Hospital said it had taken in 55 injured victims of the fire, nine of whom were in a serious condition.

Residents told AFP the renovations had begun only recently and most inhabitants were still living in the building.