A powerful explosion in the city of Ningbo, south of Shanghai, killed two people and injured at least 30 others, knocked down buildings and left streets littered with damaged cars and debris. The force of the explosion brought down buildings, shattered windows and punched holes in the walls of some residential and commercial properties nearly a mile away.

Ningbo china explosion

Firefighters have traced the blast to a hole in the ground where a toilet had been but the cause still was under investigation, state television said on its website. CCTV said the blast was not a gas explosion, as the gas pipelines beneath the ground were no longer active, citing the operator of the pipelines.

The explosion struck at around 8:50am (0050 GMT) in the Jiangbei district of the port city in Zhejiang province. According to local Zhejiang Daily, the buildings that collapsed had already been cleared of people. Police told Reuters the area had been marked for demolition. The newspaper said there were no residents at the site of the explosion, though there might have been people in the area collecting scrap for recycling when the blast occurred.

China suffers frequent deadly fires and industrial accidents, often blamed on negligence. Official safety crackdowns have improved conditions in some areas, but many companies still cut corners. In 2015, an explosion traced to improperly stored chemicals killed at least 173 people in Tianjin, a port east of Beijing.