Chinese officials say 105 miners are now known to have died in an explosion in a coal mine in Shanxi province in northern China on Thursday.
State media says the managers of the mine have been arrested for causing the accident by mining a coal seam that had not been authorised for production.
They also allegedly delayed reporting the accident for six hours while conducting their own rescue operation.
China's coal mines are among the most dangerous in the world.
The underground blast occurred at the Rui Zhiyuan mine in Shanxi province's Linfen city, state-run news agency Xinhua said. It is not clear what caused it.
Xinhua said rescue workers believed managers at the mine had tried to launch a rescue operation by themselves, "which magnified the number of casualties".
The facts of this latest mine disaster are grimly familiar, says the BBC correspondent in Shanghai, Quentin Somerville.
China - and perhaps the rest of the world - is growing used to this loss of life.
An average of 13 miners are killed every single day down the pits. In August, 181 miners were killed when floodwater poured into a mine in Shandong province in the east of the country.
Rising demand for energy and fuel means that owners and local officials often ignore safety issues in pursuit of profits.
The government has launched an ongoing safety campaign, and keeps calling for more to be done.
Officials warned recently that as mines increased output to meet increasing winter demand, accidents were even more likely to happen in the next few months.