BEIJING (AP) — An explosion at a fireworks plant in a central Chinese province killed at least 21 people and injured 61 others, state media reported Tuesday.

China’s official news agency Xinhua said the blast occurred at a fireworks plant in Changsha city of Hunan province on Monday afternoon.

Nearly 500 rescuers were deployed to the scene and people staying in danger zones were evacuated by authorities, citing high risks from two black powder warehouses at the site, the report said.

Authorities were investigating the cause of the blast but had taken “control measures” against those in charge of the company, it said, without specifying the measures.

To prevent other accidents during the operation, rescuers adopted measures such as spraying and humidification to eliminate potential hazards.

They also deployed three robots to help with the search and rescue operation.

In February, China reported two deadly explosions at fireworks shops around the Lunar New Year period.