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Officials and state media outlets say at least 50 people have been killed and over 700 more injured after two blasts, one of which was reported to be the equivalent of 21 tons of TNT, shook the Chinese port city of Tianjin late Wednesday night.

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HangZhou Night Net

The explosions, which lit up the sky with a fireball and sent a shockwave across the area, happened just after 11:30 p.m. According to the BBC, the Chinese Seismological Network registered magnitude 2.3 and 2.9 tremors.

Police in Tianjin said an initial blast took place in shipping containers at a warehouse for hazardous materials owned by Rui Hai International Logistics Limited, a “large transit distribution centre” that handles the transport of hazardous and dangerous goods.

Twelve of the dead were from among the more than 1,000 firefighters sent to fight the blaze set, the official Xinhua News agency said. It said over 520 people were being treated in hospitals, 66 of them with serious injuries.

The shockwaves were felt kilometres away, according to local media, knocking out windows in several buildings.

“I thought it was an earthquake, so I rushed downstairs without my shoes on,” Tianjin resident Zhang Siyu, told the Associated Press. “Only once I was outside did I realize it was an explosion. There was the huge fireball in the sky with thick clouds. Everybody could see it.”

Reports on social media sites such as Weibo indicate the doors and windows on homes and buildings kilometres away from the blast site were blown or shaken off, while power to many high-rise buildings in the area was knocked out. Meanwhile, Tianjin Public Security reported the East China Sea Road light rail station was damaged in the explosion.

“At the time of the explosion the ground was shaking fiercely, nearby cars and buildings were shaking, a few buildings’ glass all broke and everyone started to run,” BBC reported an eyewitness identified as Ms. Yang saying. “Now all the residents are gathered in the street.”

“Lu Yun, head of the nearby Taida Hospital, said they have received more than 50 wounded people, and more are coming. The injuries were mainly from broken glass or stones. Some of the injuries are serious,” Chinese news agency Xinhua reported.

Videos and still images circulating on social media show a massive fireball filling the night’s sky followed by a shockwave seconds after the initial explosion.

A plume of flames and smoke rose several dozen metres into the air and was reportedly caught on a Japanese weather satellite.

Ruihai Logistics said on its website – before it was shut down – that it was established in 2011 and is an approved company for handling hazardous materials. It said it handles 1 million tons of cargo annually.

Tianjin, with a population of about 15 million, is about 120 kilometres east of Beijing on the Bohai Sea and is one of the country’s major ports. It is one of China’s more modern cities and is connected to the capital by a high speed rail line.

-With files from The Associated Press.

©2015