A blast at a fireworks factory in China has killed at least 26 people and injured 61, flattening buildings and sending towering clouds of smoke into the sky, and prompting President Xi Jinping to order a thorough investigation, state media reported on Tuesday.

More than 1,500 firefighters, rescuers, medical personnel and police were deployed, together with 18 drones and several robots, to search for survivors and control on-site hazards after the explosion on Monday at a factory compound in Liuyang, the city in central Hunan province known as China’s fireworks capital.

Authorities evacuated surrounding areas because of the risk from highly combustible black powder stored in two warehouses in the complex, Xinhua reported.

The explosion happened at around 4:40 p.m. (0840 GMT) at Huasheng Fireworks Manufacturing and Display Company, according to reports by Xinhua and CCTV.

Social media footage showed smoke billowing up into clear blue skies against a backdrop of lush, green mountains. Reuters verified the location in the footage, which was posted on social media on May 4, as Changsha, the Hunan provincial capital which is responsible for the administration of Liuyang.