Ma Jinguang and Chen Zhiqiang, the chief and secretary of the party at the state-owned coal mine in Heilongjiang province, were detained (on Thursday) for alleged "dereliction of duty," the China Daily has said.
Local police and the region's coal mine safety bureau have taken documents, meeting minutes and account records from the mine as part of their investigations, according to the Xinhua news agency.
Reports of the detention came after the national work safety watchdog publicly and angrily rebuked the mine management on Wednesday for ignoring vital danger signs in the week leading up to Sunday night's explosion.
Relatives of the victims have also charged that management had no regard for safety standards at the site and had systematically exploited the miners.
Meanwhile, the death toll from the blast at the mine, which is in the bleak coal mining city of Qitaihe close to the Siberian border, continued to climb.
A total of 164 workers have been confirmed dead with another seven miners still unaccounted for, Xinhua said on Thursday, citing rescue officials.
The death toll had not been expected to rise above 151, but the owners of the mine, the state-run conglomerate Heilongjiang Longmei Group, reported on Wednesday that 20 more miners than previously reported were missing.
Investigators have said the ignition of coal dust caused the explosion.
Low safety standards
The ministry-level State Administration of Work Safety said on its website on Wednesday that the mine chiefs had held a meeting five days before the blast to discuss a dangerous build-up of coal dust in the pit.
"Your (operations) are no better than a small privately operated mine pit"
Head of coal mine administration
The head of the administration, Li Yizhong, personally interrogated and lambasted the mine's bosses, demanding to know why they did not take quick action after the danger signs were detected.
"Your (operations) are no better than a small privately operated mine pit," the website quoted Li as telling the mine chiefs.
The managers' failure to halt production after they discovered safety problems "fully shows that the mine was not up to standards in inspecting for hidden dangers," Li said.
The Longmei group is one of the biggest coal producers in China with an output of 27 million tonnes in the first half of this year.
The Dongfeng mine, built in 1956, is one of Longmei's middle-sized operations with an annual output of 500,000 tonnes.