The explosion in Liuyang, under the administration of Hunan's capital city of Changsha and a hub for fireworks manufacturing, occurred on Monday afternoon, according to reports by state media outlets CCTV and Xinhua.
Social media footage showed massive plumes of smoke billowing up into clear blue skies against a backdrop of lush, green mountains. Reuters verified the location shown in the footage, which was posted on social media on May 4, as Changsha.
A Xinhua video showed thick clouds of smoke rising from a large site littered with collapsed buildings and debris.
Five rescue teams of almost 500 personnel, together with three rescue robots, were dispatched to the scene, adopting a "human-machine co-ordinated approach" to conduct grid-style searches, according to Xinhua.
Two black powder storage warehouses within the factory compound posed high-risk hazards, the report said, adding that authorities had evacuated residents from danger zones, established a 1km rescue area and a 3km control zone.
The blast happened at Huasheng Fireworks Manufacturing and Display Company, state media said.
The person in charge of the company has been detained and the cause of the accident was being investigated, state-run China Daily reported.
Xi called for a speedy investigation to determine the cause of the explosion and strict accountability for the incident, Xinhua reported.
In 2025, China exported $US1.14 billion ($A1.59 billion) worth of fireworks, more than two-thirds of global sales, data from the Observatory of Economic Complexity showed.
Xi also ordered authorities to strengthen risk screening and hazard control in key industries, enhance public safety and ensure the safety of people's lives and property.
Xi often issues "important instructions" to local officials after major accidents and disasters with fatalities.
Last week, he urged a nationwide upgrade in China's disaster response capacity.
Xi also issued instructions after a fire tore through several residential towers in Hong Kong's Wang Fuk Court complex in November killing 168 people.
With AP
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