The plant, situated in an industrial park, manufactures chemical components for use in pesticides and pharmaceuticals, they said.

Videos circulating on Chinese social media and verified by the Reuters news agency showed plumes of orange and black smoke billowing into the sky.

Windows of nearby buildings were ripped from their hinges by the explosion, one of the videos showed.

Authorities launched a large response to the explosion and the blaze it ignited, with officials sending more than 230 responders to the scene, according to CCTV.

Drone video posted by The Beijing News, a government-run publication, showed smoke emerging from the chemical plant and from a second, unidentified facility nearby.

Baidu Maps, a navigation app, shows other manufacturing companies next to Youdao’s plant, including a textile company, a machinery company and a firm that makes industrial coating materials.

The Weifang Ecological Environment Bureau dispatched staff to test the site of the blast, but said no results were available yet. It advised nearby residents to wear face masks in the meantime, The Beijing News reported.

A local resident, who did not wish to be identified for fear of repercussions, said in a video that his home, more than 7km (4.3 miles) from the plant, shook from the impact of the explosion, The Associated Press news agency reported.