A deadly blast that rocked China’s port city of Ningbo at the weekend was caused by the mishandling of illegal explosives, police said Tuesday.

Sunday’s blast hit a crumbling light-industrial area after a fugitive wanted for manufacturing and selling illegal explosives had asked relatives to dispose of the material, Ningbo police said in a statement.

This file picture taken on November 26, 2017 shows rescue workers searching at the site of an explosion in Ningbo, China’s eastern Zhejiang province. Photo: AFP/Stringer.

The explosion killed two people and injured at least 19 in the city, which is just south of Shanghai and one of China’s largest ports. Two others were reported missing.

The 33-year-old suspect surnamed Shan, who had been wanted by police in the northeastern province of Liaoning since late October, was arrested on Monday night. He had been hiding in the central province of Hubei, police said.

They did not indicate why the suspect had been making explosives, which were shipped from Liaoning to Ningbo and contained aluminium powder and barium nitrate.

The explosion happened after his relatives took the material to the site on Saturday, the statement said.

They began to dismantle the explosives that same night and continued on Sunday morning, when the material blew up. The police statement did not say how many people were involved or what happened to them.

The local government had said Monday that a septic tank in a vacant lot was at the epicentre of the blast.

“Investigation showed the careless handling process could have caused the explosion and excluded the possibilities of any intentionally man-made blast,” police said.

The local government and state media variously described the site as a vacant lot or an abandoned factory.

The force of the explosion shattered windows in nearby apartments, mangled cars and reduced small buildings to rubble, though locals said the structures were already in poor shape and slated for demolition.

The explosion was so powerful that it was heard several kilometres away.

Residents said some people from outside Ningbo had been squatting at the site, but others disputed that.

In addition to the fatalities, four people were severely injured and 15 others slightly hurt.

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