The Federal Security Service (FSB) of Russia announced on Monday that it had discovered evidence of explosives on a ship transporting grain from Turkey to Rostov-on-Don.

The ship, according to the FSB, may have been used to transport explosives to Ukraine when it was berthed in the Ukrainian port of Kiliia in May.

It said the ship had changed its name while in the Turkish port of Tuzla earlier this month and replaced its crew, which had consisted of 12 Ukrainian nationals.

“These circumstances may indicate the possibility of using the foreign civilian ship to deliver explosives to the territory of Ukraine,” it said.

The vessel, which it did not name, had been inspected in the Kerch Strait and was banned from continuing its journey, after which it left Russian waters, the FSB said.

Reuters could not immediately confirm the details of the FSB statement. It came one week after Russia pulled out of an agreement that had enabled Ukraine to export grain from its Black Sea ports, with ships undergoing security inspections.