The death toll from a massive explosion at a chemical plant in eastern China has risen to at least 64, with hundreds of others injured, 90 of them seriously, ABC says.

Rescuers pulled a survivor from rubble early on Saturday (local time), more than 24 hours after the blast at the factory, which had a long record of safety violations.

The number of deaths appeared likely to rise still further, with another 28 people still listed as missing, the official Xinhua News Agency reported.

Just 26 of those confirmed dead in Thursday's explosion have been identified, it said.

The blast in an industrial park in the city of Yancheng, north of Shanghai, was one of China's worst industrial accidents in recent years.

State-run television showed crushed cars, blown-out windows and workers leaving the factory with bloodied heads.

Windows in buildings as far as six kilometres away were blown out by the force of the blast, which caused a magnitude-2.2 seismic shock.

A woman, who only gave her surname, Zhi, said she lived about five kilometres from the plant and that glass from windows smashed by the force of the blast injured her neighbours.

Schools were closed and nearly 1,000 residents were moved to safety as a precaution against leaks and additional explosions, the city government said.