Ukraine`s safety agency says dozens of miners caught in an explosion that killed at least one this week had violated a work ban that was imposed due to dangerous methane levels, according to AP.

Officials originally said the miners were underground to improve safety conditions. But safety agency spokesman Andrian Halach says audio tapes "prove that coal-mining took place on that day."

The Karl Marx mine, where seven died in a 1999 blast, was one of 23 where work was suspended last week for safety violations. Miners were permitted to enter the mines for safety work but not for extraction.

Safety agency spokeswoman Maryna Nikitina said 12 miners remained missing Tuesday, two days after the blast; 24 others were brought to the surface, five of whom remained hospitalized.