Iran’s military struck a container ship in the Strait of Hormuz on Thursday, according to a U.S. official, undermining efforts to restore shipping traffic through the crucial waterway.

The ship, the Ever Lovely, was attacked after Iran agreed last week to let shipping pass through the strait safely.

The strike, which took place when the ship was near the coast of Oman, prompted a United Nations agency, the International Maritime Organization, to pause an evacuation of hundreds of ships that had been stranded in the Persian Gulf during the U.S.-Israeli war on Iran.

A spokeswoman for the maritime organization said the Ever Lovely had not coordinated its passage with the agency’s evacuation effort.

In recent days, ship traffic through the strait surged as shipping companies calculated that the waterway had become safer after the United States and Iran signed a memorandum of understanding last week to try to find a lasting peace.

Around 70 vessels transited the waterway on Wednesday, including 29 tankers, making it the busiest day since March 1, the day after the war began, according to Kpler, a maritime data company. But earlier Thursday, the naval arm of Iran’s Islamic Revolutionary Guards Corps said in a statement that only routes announced by Iran were authorized, warning ships against using any other corridor. Many ships have been using a route on the southern side of the strait, hugging the Omani coast.

The Ever Lovely is owned by Evergreen Marine, a large shipping company based in Taiwan, according to Equasis, a ship data base.

This is a developing story. Check back for updates.

Jenny Gross and Rebecca F. Elliott contributed reporting.