(LI ZIHENG)

Firefighters search for the missing people after a leaking pipeline caught fire and exploded on November 22 in Huangdao District , Qingdao, a coastal city in east China's Shandong Province.

As of November 27, the blasts had killed 55 people, injured 145 others and left nine missing.

At 3 a.m. on November 22, crude oil began leaking from an underground pipeline operated by Sinopec, the country's largest oil refinery. The spill then flowed into the city's rainwater pipe network. Explosions ripped through residential and commercial roads in Huangdao at around 10:30 a.m. on the day when workers were clearing the spill.

The blasts exposed severe problems caused by human error and involved "very serious dereliction of duty," according to Yang Dongliang, Director of the State Administration of Work Safety and head of an investigation team for the accident.

Nine people had been put in police custody, including seven from Sinopec and two from Qingdao's economic and technological development zone, said police investigating the accident on November 26. The rescue headquarters announced on November 27 that they will permanently shut down the explosion-hit oil pipeline.