The International Maritime Organization, a specialized United Nations agency, said Thursday it has temporarily paused its evacuation operation in and around the Strait of Hormuz after a vessel was attacked in the Gulf of Oman.

A US official told CNN the ship was hit in an Iranian drone attack, but did not provide further details. Iran has not claimed responsibility.

The pause comes days after the IMO said an agreement between the United States and Iran had opened the way for the evacuation of more than 11,000 stranded seafarers from the Persian Gulf region.

“Following the launch of the IMO’s evacuation plan, through which several vessels have already been successfully evacuated, I have decided to temporarily pause its implementation in order to reconfirm that the necessary safety guarantees continue to be in place for the ships on our evacuation list and all those in the region,” IMO Secretary-General Arsenio Dominguez said in a statement.

He said he had been informed of an attack Thursday in the Gulf of Oman on a vessel that had passed through the Strait of Hormuz, adding that the ship was not operating under the IMO evacuation framework.