Authorities in China on Sunday were still searching for two missing people and investigating a coal mine operator, after at least 82 people were killed in a gas explosion in a mine shaft on Friday.

A total of 247 miners were reportedly underground at the time of the blast at the Liushenyu coal mine in the northern inland province of Shanxi, with 128 subsequently taken to hospital.

While rescue teams continued to search for two missing people with the help of a robot which was sent into the shaft to test conditions, local officials accused the mine operator of "serious breaches" of security regulations.

A spokesman wouldn't specify what exactly the breaches were, but information reported by local media suggests several cases of operative negligence.

China coal mine: 'Chaotic' scenes and 'inaccurate' information

Some miners told the AFP news agency that they had had to purchase protective helmets with their own money while another report suggested that over half of the miners entered the mine shaft on Friday without having been properly registered with face recognition or issued with requisite tracking devices.

Officials have blamed "chaotic" scenes and "inaccurate" information provided by the mine operator for an initial death toll of 90, which had to be revised downwards, while state broadcaster CCTV reported that blueprints provided by the coal mine did not match the actual layout, hampering rescue efforts.

State media outlet Xinhua said one "responsible person" had been "placed under control" while the government in Beijing ordered a nationwide clampdown on "illegal and illicit activities," such as the falsification of security data, inaccurate tracking of miners' activities and illegal commissioning procedures.

Xi Jinping calls for 'thorough' investigation

Chinese President Xi Jinping called for a thorough investigation while a commentary in the official People's Daily newspaper on Sunday called for all regions and departments to learn from the accident and to "always keep safety in mind."

Shanxi Province is one of China's poorer regions and the center of the country's coal production. Despite the rapid expansion of renewable energies, China has the highest coal consumption in the world.

Mining safety in the country has improved over the past few decades; nevertheless, accidents continue to occur. In 2009, 108 people lost their lives in an explosion at a mine in the northeastern province of Heilongjiang.

Edited by: Jenipher Camino Gonzalez