At least 123 people were trapped underground on Sunday after water gushed into a coal mine in northern China, a government agency said.

The Wangjialing coal mine in Shanxi province was flooded by underground water as 261 miners were working in the pit, the State Administration of Work Safety said on its Website.

The administration said 138 of the miners were lifted safely to the ground but the others remained trapped and rescue work was under way. It said the cause of the flood was still under investigation.

The mine is located between Xiangning county and the city of Hejin and covers an area of 180 sq. km, the official Xinhua News Agency said. Calls to the mine rang unanswered.

State broadcaster CCTV said the heads of the country’s coal mine and work safety administrations were leading a team of workers on their way to the site to assist with rescue efforts.

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