Ukrainian Defense Minister Stepan Poltorak has ordered an examination of the metal from which an M-15 Molot mortar was produced as part of an official investigation into the deadly accident that occurred at the Rivne combined arms firing range, the press service of the Ukrainian Defense Ministry reported on Monday.

Poltorak ordered an examination to be conducted at the research laboratory of the Kyiv Polytechnic Institute.

The samples have currently been transferred to the research laboratory, where they are being examined.

"Conclusions on the results of the examination will help establish the objective cause of the mortar explosion," the ministry said.

As earlier reported, at least three Ukrainian soldiers were killed and nine more were wounded in a deadly accident during military drills at the Rivne firing range on July 6.

The deaths were reportedly caused by the premature explosion of a mortar round during gunnery drills. Another nine soldiers sustained injuries of varying severity.