Ukraine's State Security Service says two men have been arrested on suspicion of involvement in the operation of an illegal tunnel across the Ukraine-Slovakia border.
Officials said the pair was arrested this week in the Crimean city of Evpatoria.
Slovak and Ukrainian border guards last month said they discovered the underground tunnel connecting the countries.
There are suspicions that the tunnel may have been used for the illegal transit of humans and goods.
Officials said the tunnel stretched for about 70 meters on the Ukrainian side of the border.
Based on reporting by UNIAN and Interfax