The US Navy spotted what it suspects was an unexploded limpet mine attached to one of the two tankers attacked on Thursday.

US Central Command (CENTCOM) later released photos of the mine, as well as video evidence of the crew of an Iranian gunboat attempting to take it.

The mine, which was discovered by the USS Bainbridge, is a potential smoking gun because it very likely points to Iran's involvement in the attack on the commercial vessels.

Iranian forces are not only suspected of using limpet mines in the attack on four tankers last month, but Iran also used mines in the Tanker Wars in the 1980s.

The US pinned the blame for the attack on Iran Thursday afternoon. The announcement sent the US West Texas Intermediate crude futures surging to $52.88 per barrel, or up 3.4% from the day's start.

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The US is accusing Iran of carrying out attacks on two tankers just outside the Strait of Hormuz, a critical waterway through which more than 30% of the world's seaborne crude oil passes. The US Navy discovered an unexploded mine that appears to be evidence of Iran's culpability in Thursday's attacks.

The USS Bainbridge, a US warship deployed to the Middle East, spotted a triangular-shaped limpet mine, a weapon with which Iran is believed to be very familiar, on the side of the Kokuka Courageous, one of two targeted tankers. US Central Command (CENTCOM) has released photos of the suspected mine.

Secretary of State Mike Pompeo said Thursday afternoon that Iran was responsible for the attacks, an announcement that briefly spiked US West Texas Intermediate crude oil futures up to $52.88 per barrel, or 3.4% from the day's start.

The secretary did not provide specific evidence for the accusations but said US conclusions were "based on the level of expertise for the execution, and recent attacks on shipping, and the fact that no proxy group operating in the area has the resources and proficiency to act with such a high degree of sophistication."

CENTCOM offered possible evidence of Iranian involvement in the attacks a few hours later.

Not only did the crew of USS Bainbridge, an Arleigh Burke-class guided-missile destroyer, take photos of the limpet mine, it captured video evidence of the crew of an Iranian gunboat taking the unexploded mine, US Central Command said in an emailed statement.

A limpet mine is a type of explosive with a detonator that can be attached to the hull of a ship using magnets, and Iranian forces are believed to have used these weapons in an attack on four oil tankers off the coast of the United Arab Emirates in May. While the US has blamed Iran for the attacks, Tehran has repeatedly denied any involvement.

The UAE, without naming any names, determined that a "state actor" was behind the tanker attacks and concluded "it was highly likely that limpet mines were deployed."

There has been some debate about who was behind the latest attacks, with one US official telling ABC News early Thursday that "we're not pointing to Iran, but we're not ruling anything out at this time." But, another official asked, "Who else could it be?"

Iran used mines heavily during the "Tanker Wars" in the late 1980s.

Florida Sen. Marco Rubio, who may have been briefed on the situation at the time of his comments, was quick to pin the blame on Iran's Revolutionary Guard Corps, telling reporters: "I saw some press accounts today sort of saying it's not clear who did it. Well, it wasn't the Belgians. It wasn't the Swiss. I mean, it was them. They're the ones that did it. We've been warning about it."

In early May, the US began deploying military assets to the Middle East as a deterrence force in response to intelligence indicating that Iran was planning attacks on US interests, including commercial shipping. The US has so far sent a carrier strike group, a bomber task force, a missile-defense battery, and a number of other capabilities into the CENTCOM area of responsibility.

"The U.S. and our partners in the region will take all necessary measures to defend ourselves and our interests," a CENTCOM spokesman said in a statement Thursday. "Today's attacks are a clear threat to international freedom of navigation and freedom of commerce. The U.S. and the international community, stand ready to defend our interests, including the freedom of navigation."



"The United States has no interest in engaging in a new conflict in the Middle East. However, we will defend our interests," the spokesman added."

This post was updated to reflect the latest information from CENTCOM.