Police in China have arrested nine people over a deadly oil pipeline blast in the eastern city of Qingdao that killed 55, various reports said Tuesday.
The BBC said seven of those detained worked for Sinopec, which owns the pipeline. The other two were city employees.
At least 160 people were injured in Friday's explosions, that were caused when crude oil leaking from the pipeline caught fire in a densely populated area of the city. Many of the dead were workers trying to clean up the spill.
Nine people are still missing.
Chinese President Xi Jinping ordered surprise inspections of the country’s oil and gas pipeline network after visiting the port city on Sunday to check on rescue efforts and visit victims.
“A large-scale work safety check should be launched ... with inspectors going deep into the production sites anonymously and unannounced," the official Xinhua news agency quoted Xi as saying.
More from GlobalPost: China oil pipe blast kills 35 (PHOTOS)
China Petroleum & Chemical Corp, otherwise known as Sinopec, has apologized for the accident, which government officials have blamed on human error.
“We are deeply sorry for what has happened in Qingdao and express our sincere condolences to the victims and their families,” Sinopec Chairman Fu Chengyu said on his company’s microblog, Bloomberg reported.
“We will do our very best to assist in rescue and post-disaster efforts and work with government investigators to find out the cause.”
The official Xinhua news agency on Monday quoted Yang Dongliang, director of the State Administration of Work Safety, as saying the accident was a "very serious dereliction of duty."
Yang highlighted the "unreasonable layout of the oil pipelines and urban drainage pipes" and the "unprofessional handling" of the oil leaks before the blasts.
"The pipe was not properly maintained, leading to the original oil leak, and following the leak the emergency procedures were insufficient. They did not take preventative measures such as sealing off the area and evacuating people," Yang said.
The oil leak was detected hours before the blasts but residents were not warned.
"It felt like an earthquake, and I was dumbstruck," said Gao, a resident of Qingdao who was driving past the district where the explosions occurred when he felt the blasts and saw the ground in front of him fracture.
The explosions were China's third deadliest industrial accident this year, after a chicken factory fire in June that killed 121 and a mining accident in March that left 36 dead.