Traces of explosives were discovered on Monday, July 24, according to Reuters, by Russia’s Federal Security Service (FSB), on a ship sailing from Turkey to the port of Rostov-on-Don to get grain.

The official Russian news agency, citing the FSB, says the ship had docked at the Ukrainian port of Chilia in May and could have been used to deliver explosives to Ukraine.

The announcement comes a week after Russia pulled out of an agreement that allowed Ukraine to export grain from Black Sea ports, with ships subject to security inspections.

“On July 22, in the hold of a foreign cargo ship on its way from Turkey to the port of Rostov-on-Don to load grain, traces of explosives – dinitrotoluene and tetryl – were found. Evidence of interference was also found in the ship’s structural parts,” the FSB said in a statement to TASS.

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

“These conditions may indicate the possibility of using the foreign civilian ship to deliver explosives to Ukraine,” according to the FSB.

The ship, which has not been named, was inspected in the Kerch Strait and prevented from continuing its journey. It then sailed out of Russian waters.

Reuters could not immediately confirm the details of the FSB’s statement.