Port authorities tried to right a capsized ship on Monday to rescue thousands of sheep trapped below deck in the Black Sea off Romania.
The Palau-registered Queen Hind flipped onto its side shortly after leaving Romania's Midia port en route to Saudi Arabia on Sunday. Its crew, most of them Syrians, were rescued.
"There are hopes to rescue many sheep, as they are trapped under the deck in air pockets," an officer from Romania's naval authority said, speaking on condition of anonymity.
"But operations to lighten the ship and refloat it are very difficult and may last several days," the officer added.
Drone footage released on the BBC showed the bodies of dozens of drowned animals floating next to the vessel.
Just 50 of the ship's estimated load of 14,000 animals have been rescued so far, the naval official said. Several tugboats and other vessels were involved in the operation, they added.
Agriculture minister Nechita-Adrian Oros said his department, the transport ministry and the national food and animal safety watchdog had launched an investigation into why the ship capsized.
Romania is the European Union's biggest exporter of live sheep to the Middle East. Animal rights groups have criticised conditions on vessels and said some are overloaded.
Reporting by Radu Marinas