MOSCOW, Reuters – Siberia’s police said Friday they arrested two Siberian safety inspectors accused of criminal negligence and leading to death. The incident occurred as Russia’s largest coal mining region was mourning one of the most devastating natural disasters in its history.

The Emergencies Ministry has confirmed that 52 people were killed by a gas leak at a Kemerovo coal mine on Thursday. Six rescuers also went down to help dozens more men trapped deep below the ground.

According to the Investigative Committee (a committee that investigates serious crimes), the inspectors detained had issued a safety certification for the mine in Nov, but hadn’t actually checked it.

It stated in a statement that the inspectors will be taken into custody and soon charged.

The director of Listvyazhnaya’s mine and his assistant were among three other individuals who were taken into custody late Thursday.

Regional governor said that three miners died and three rescue workers were killed when emergency personnel had to stop rescue operations the day prior due to the danger of explosion.

According to the TASS news agency, four people were being treated in intensive care, one of them being a rescue worker. According to it, 50 were admitted to hospital.