The explosion occurred after oil leaked from the pipeline into Qingdao’s municipal rainwater network.
The China police have arrested nine people of which seven belongs to the pipeline owner China Petroleum & Chemical and the other two from an economic and technological development zone of Qingdao.
The state media reported that, 11 people were missed and 136 remain in hospital.
Qingdao, which is one of country’s largest crude oil import terminals, has involved in supplying to Sinopec refineries, Qingdao plant and Sinopec Qilu Petrochemical, as well to small and independent refineries.
Sinopec was quoted by Reuters, as saying that the explosion was caused by a leak in the Huangwei crude oil pipeline.
The local government said the oil had spilled into the port, which also caught fire, and had spread across 3,000m² of sea water.
"Early investigations showed the spilled oil flowed into the municipal grid, which caused the explosion," added local government.
According to news agency Xinhua, China President Xi Jinping said to local authorities, "spare no effort to rescue the injured and strengthen safety to eradicate such incidents."
