The country's top military leadership is contributing to the investigation of the case of the breakthrough of Russian troops in Kharkiv region, in order to identify the perpetrators, it is necessary to study secret documents, said Oleksandr Udovychenko, First Deputy Director of the State Bureau of Investigations (SBI).

In an exclusive interview with Interfax-Ukraine, he said that in order to establish the truth in the case of the breakout of the occupiers in Kharkiv region, investigators and experts need to examine a lot of documents.

"All these documents are classified. What does this entail? A complicated procedure for their seizure, receipt, and access to documents of investigators and experts. There are a lot of these documents, they are specific, they are in different places, and some are simply impossible to withdraw, because now they are being used – without them, some processes on the front line may be paralyzed," Udovychenko said.

According to the first deputy director of the SBI, 104 people have now been questioned in the case.

"These are the military leadership, the fighters who were directly on the battlefield, and many other people. Some were interrogated three or four times," he said.

Answering a clarifying question about whether the initial appearance of information about a criminal case with reference to the register of court decisions, and not to the SBI, means a desire to hide the fact of the investigation itself, Udovychenko said: "Decisions in the register of court rulings can simply be closed. Firstly. Secondly, the registry is a good tool for sending a message to society: please, read it, we are not hiding, we are investigating. The fact that we did not close this court decision, means that we did not hide the fact of criminal proceedings."

The first Deputy director of the SBI assured that the case would be investigated objectively as soon as possible.

"The relevance and importance of the case is obvious. On a weekly basis, the leadership of a law enforcement agency visits the site to monitor the progress of the investigation. As the organizer of the investigative process, I am very grateful to the commander–in-chief - he contributes to the investigation, is interested in figuring it out," Udovychenko stressed.

He drew attention to the fact that according to the law, if the court's decision on temporary access is not enforced, then investigators have the right to come with a search. "Let's simulate the situation: a search at a high-security military facility during the war. This is too much," he added.

"Thus, I am sure that if there was no will, no desire to establish the truth, there would be a lot of excuses not to give us documents. Full openness and assistance help in the speed of the investigation," said the first deputy director of the SBI.