The two workers injured in the oil tank blast at a refinery in Dalian on Sunday have died, sources from the Dalian Administration of Work Safety said on Monday afternoon.

Four workers from a local construction engineering company were replacing the instrument platform of the No 939 oil tank, when there was a sudden explosion.

The other two men are still missing, and the cause of the blast is being investigated.

According to Xinhua, three other tanks also caught fire.

There are 18 such tanks used to store phenylethane and other materials at the Dalian plant of the China National Petroleum Corp.

The plant stopped manufacturing such products in March 2012, and the tanks were suspended from use two months later.

This year, in accordance with the risk management plan, the CNPC Dalian plant entrusted CNPC’s seventh construction company to replace the instrument platform of the No 939 oil tank. The latter entrusted it to Dalian Linyuan Construction Engineering Co Ltd, which employed the four workers.