The United Nations’ International Maritime Organization (IMO) has suspended its plan to assist hundreds of stranded ships and thousands of sailors through the Strait of Hormuz, following an attack on a vessel in the Gulf of Oman.

The vessel, the Singapore-flagged Ever Lovely, was struck near Oman, according to the British military’s UK Maritime Trade Operations (UKMTO) service, just hours after Tehran warned ships not to use routes that had not been approved by Iranian authorities.

A security source said the vessel was most likely targeted by a drone. The ship was not participating in the evacuation program.

There was no immediate comment from either Iran or the United States regarding the incident, according to Reuters.

The IMO had been helping hundreds of stranded vessels and thousands of seafarers leave the Strait of Hormuz, where they had been trapped for months since the outbreak of the war in late February.

The organization stated that it had decided:

“to temporarily suspend implementation of the program in order to reconfirm that the necessary safety guarantees remain in place for the vessels on our evacuation list and for all ships operating in the area.”

The initiative, launched on Tuesday, was a voluntary program allowing ships and their crews to depart the Gulf via two designated routes—one through Iranian waters and the other through Omani waters—under U.S. supervision.

Oil prices rose by 1.9% following the attack. According to analysts, the incident renewed concerns over how long it may take for oil flows through the Gulf to return to normal levels.