Military investigators opened a criminal case Wednesday in connection with a deadly explosion at a military training facility in the Pskov region.

The investigation department said in a statement that the blast, which Tuesday killed six paratroopers and wounded two others, was caused by an explosion from an eroded weapon not far from where troops were setting up a target, Interfax reported.

The investigation is now looking into possible violations of firearm regulations, an offense which carries up to a 10-year prison term if resulting in the death of two or more people.

The shockwave, the wounds sustained by the victims and the crater left by the blast all indicate that an artillery shell had gone off, the Defense Ministry said.

The ammunition was most likely lying in a heap on the side of the road for a long time, said Ivan Buvaltsev, director of the military's combat training department. He added that the Strugi Krasniye fields are used by multiple military branches for training exercises, and experts would determine where the shells came from.

The two wounded men were evacuated to St. Petersburg for shrapnel wounds and were in critical condition Tuesday night. The Defense Ministry said Wednesday that the pair were no longer in life-threatening danger.

Defense Minister Sergei Shoigu asked the authorities to provide all required assistance to the victims' families.

Criminal Case Opened in Pskov Military Training Explosion