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 on Monday at around ​4:40 p.m. (0840 GMT), 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 1 km ‌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 $1.14 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.