HONG KONG, May 5 (Reuters) - A blast at a fireworks factory ‌in China's Hunan province has killed 21 people and injured 61, prompting a ​call from President Xi Jinping for a thorough investigation, state media reported on Tuesday. The explosion in Liuyang, under the administration of Hunan's capital city of Changsha and a hub for fireworks manufacturing, occurred yesterday ​at around 4.40pm (4.40pm Malaysian time), according to reports by 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 nearly 500 personnel, together with three rescue ⁠robots, were dispatched to the scene, adopting a "human-machine coordinated 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 3 km control ⁠zone. The blast happened at Huasheng Fireworks Manufacturing and Display Company, state media said.

Reuters could not find a telephone listing for the company to seek comment.

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.

Last year, China exported US$1.14 billion (RM4.5 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. — Reuters