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Chinese authorities have arrested 12 people in the aftermath of a series of deadly blasts that rocked the city of Tianjin two weeks ago, state media reported Thursday.

Yu Xuewei, the chairman of the company that owns the warehouse that exploded Aug. 12, Tianjin International Ruihai Logistics Co. Ltd., was among those arrested, state media agency Xinhua reported, citing police.

Vice chairman Dong Shexuan and three of the company’s deputy managers were also arrested, Xinhua reported.

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On Wednesday, China's head of work safety was fired and named as a suspect in a corruption investigation, Xinhua reported. Yang Dongliang, 61, was suspected of "severe violation of discipline and law," the state media agency said. No other details were provided.

The pair of powerful explosions sent a fireball high in the sky and devastated a large swath of port area of Tianjin, about 75 miles southeast of Beijing. Windows were blown out in buildings more than a mile away. The blasts left at least 139 people dead.

Related: Tianjin Toxic Blasts Put China's Communist Party On Spot

The government confirmed last week that there were about 700 tons of the deadly chemical sodium cyanide in the warehouse before it exploded at around 11:30 p.m. local tome on Aug. 12.

Among other chemicals stored at the warehouse were 1,300 tons of potentially explosive oxidizing chemicals, including ammonium nitrate and potassium nitrate, 500 tons of flammables, including sodium and magnesium, and 700 tons of deadly poisons, mainly sodium cyanide, Reuters has reported.

The Tianjin Environmental Protection Bureau said last week that tests showed cyanide levels in the river, sea, and waste water in the evacuated area around the disaster zone had sharply risen since the blasts.

One testing site at the mouth of a rain water pipe recorded cyanide levels 356 times above acceptable standards, the bureau said. Officials said drinking water was safe, however.

Greater Tianjin is home to around 15 million people, according to government figures.