The period of the preliminary investigation into the case involving the Ukrainian sailors detained in the Kerch Strait has been prolonged by another two months due to the need to conduct certain investigative actions, Nikolai Polozov, a lawyer for the accused, told Interfax on Wednesday.

"The investigation has been prolonged by two months because the investigator needs to receive answers to requests from operatives. The investigators also plan to question a witness, they are not saying which," Polozov said.

The lawyer said the investigators do not plan any investigative actions with the sailors and have no intention of summonsing them.

The defense lawyers can continue reading the case materials after being notified about the completion of the investigative actions, Polozov said.

All property seized from the Ukrainian ships now remains in Russia as physical evidence, he said.

He earlier said the equipment and weapons taken from the ships could be transferred to Ukraine to be impounded by the Ukrainian authorities.