Ten people have been rescued from the Red Sea after their ship sank near Yemen following an attack by the Houthis, according to the European Union’s maritime security mission, with several others believed to be being held by the rebel group.

The death toll from the attack that sank the Liberian-flagged Eternity C ship is the highest from any seaborne assault carried out by the Iranian-backed rebels in the crucial maritime trade route.

Houthi rebels have attacked and sunk the cargo ship Eternity C in the Red Sea. A European naval force reported Wednesday that only six of the 25 crew members have been rescued so far.