The detention of the vessel is a new twist in a grain war that erupted between Russia and Ukraine following Moscow’s February 2022 invasion of its neighbor. For months thereafter, Ukraine was unable to export its crops through the Black Sea. A U.N.-brokered deal allowed exports to resume for a time before collapsing last July.

Ukraine subsequently managed to reassert control over the western reaches of the Black Sea and reopen its maritime export route. But Kyiv and Moscow remain at odds over “stolen” grain exported from Russian-occupied territory through ports in Crimea.

The Cameroon-flagged vessel was intercepted this week at Reni, a Ukrainian port on the lower reaches of the Danube River.

Ukrainian investigators argue the ship’s crew knew they were violating international law, because before entering Sevastopol they switched off the ship’s automatic identification system — making its movements harder to track.

The prosecutors detained the vessel on the basis of a court order. On board they discovered documents issued by the Sevastopol trade port administration to the crew. The ship’s captain, an Azerbaijani citizen, is also suspected of illegally crossing the border of the occupied part of Ukraine, the investigators said.

The Ukrainian court must now decide what measures to take against the ship’s captain, and must turn the vessel over to a state agency that handles seized assets.