According to the rescue headquarters, an initial investigation showed that the cause of the accident was the local gas explosion underground.

据事故抢险指挥部介绍，现已初步查明，事故原因为井下局部瓦斯爆炸。

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An underground organization has claimed responsibility for the bomb explosion.

一个地下组织已声称对炸弹爆炸事件负责。

《柯林斯英汉双解大词典》

The site of the first explosion was only 120 metres underground, but 2km from the mine’s entrance.

第一次爆炸发生的地点仅在地下120米处，但却离出口有两千米远。

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Twenty-nine of them died in an explosion at an underground mine in West Virginia on April fifth,twenty-ten.

VOA: special.2011.07.01

Panetta said U.S. technical experts are still assessing available data to learn more about the underground explosion.

NPR: Kerry: Response To NKorea Will Send Iran A Message

North Korea confirmed the test after international monitors recorded seismic activity consistent with a powerful underground explosion at 11:57 (02:57 GMT) on Tuesday.

BBC: North Korea nuclear test branded 'serious threat' to US

"Highly enriched uranium is something that degrades quickly, so you would have to collect within a 24-hour period, " especially because the traces from an underground explosion will be minimal, he said.

NPR: NKorean Nuclear Test May Be Intelligence Windfall