Managers of the operation were detained after they failed to report the accident for more than a day.
The mine in Qixia, a jurisdiction under the city of Yantai in Shandong province, had been under construction at the time of the blast, which occurred January 10.
More than 300 workers are seeking to clear obstructions while drilling a new shaft to reach the chambers where the workers were trapped and expel dangerous fumes.
Keep on with the rescue efforts. We have hope, thank you," read the note, written in pencil on notebook paper and posted on Xinhua's official website.
China's mining industry has a reputation for skirting safety requirements amid massive demand for coal and precious minerals, although increased supervision has reduced the frequency of accidents that used to claim an average of 5,000 miners per year.
Two accidents in the southwestern megacity of Chongqing last year killed 39 miners, prompting the central government to order another safety overhaul.
(Only the headline and picture of this report may have been reworked by the Business Standard staff; the rest of the content is auto-generated from a syndicated feed.)
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