The United States released footage on Thursday of what it claimed to be Iranians removing an explosive device that did not go off from the hull of one of the two tankers hit the same day in the Gulf of Oman.

The video, reportedly taken by the USS Bainbridge, shows what the United States claimed to be an Islamic Revolutionary Guard Corps Gashti Class patrol boat going to the side of the Japanese-owned Kokuka Courageous tanker, with a crew member apparently removing the item from the hull—proof, according to a U.S. official, that Iran was responsible for Thursday’s attacks, which also consisted of an attack on the Norwegian-owned tanker Front Altair.

U.S. Secretary of State Mike Pompeo blamed Iran for Thursday’s attacks.

“It is the assessment of the United States government that the Islamic Republic of Iran is responsible for the attacks in the Gulf of Oman,” he said at a press briefing on Thursday afternoon at the U.S. State Department.

The Japanese operator of the Kokuka Courageous tanker that was damaged in the attack says all of its crew members were now safely aboard the Bainbridge.

The Bainbridge crew said that they saw the unexploded “limpet mine” on the side of one of the ships attacked, reported CNN, citing a U.S. defense official familiar with the situation.

Thursday’s attacks came less than a month after Iran was blamed for attacking four oil tankers off the coast of the United Arab Emirates.