At least 12 people died and more than 300 were injured by a powerful explosion triggered when a chemical pipeline ignited in eastern China on Wednesday, state media said.
Footage broadcast on state television showed a billowing column of flame and a plume of thick black smoke drifting over the city of Nanjing after the blast, which toppled nearby factory buildings.
The blast occurred in Nanjing, capital of Jiangsu province, shortly after 10.00am (0200 GMT) and caused heavy damage to the surrounding area, reports said.
Many hospitals had almost exhausted their blood stocks and local residents were rushing to mobile collection vehicles to donate blood, the official Xinhua news agency said.
"Many residents have been injured and sent to hospitals, we urgently need a lot of blood," the Jiangsu provincial blood centre appealed on its website.
State television said 12 people had died, without saying where the information was obtained from.
Xinhua said earlier its reporters had seen six people recorded as dead at nearby hospitals.
The explosion reportedly occurred on the grounds of an abandoned plastics factory when a pipeline carrying ethylene blew up.
The blast also blew out windows and caused damage to businesses and residences up to 300 metres away, while people further away fled their buildings, thinking an earthquake had struck.
More than 300 people were rushed to local hospitals for treatment, including 52 with serious injuries, the China News Service said. State television put the injured at more than 100, 15 of them seriously.
The explosion hit a bus passing through the area, injuring many passengers, Xinhua said.
Photos posted on the internet showed at least one bus that had been completely burnt out, leaving only a charred skeleton.
"There are dozens of injured in our hospital. Their situations are not serious, most of them suffered burns," said a doctor at the city's Zhongda hospital, who refused to identify herself.
"Nobody has died in our hospital. There are injured people in every big hospital in Nanjing."
Xinhua said the fire triggered by the blast had been brought under control.
Deadly industrial accidents are routine in China, where basic safety provisions are often ignored.
Last week, an oil pipeline exploded in the northeastern port city of Dalian, triggering a spectacular blaze that burned throughout the weekend and spilled about 1,500 tonnes of oil into the Yellow Sea off Liaoning province.
The incident was one of China's worst-ever oil spills.
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