Iran’s military loaded naval mines onto vessels in the Persian Gulf last month, raising concerns within Washington that Tehran was preparing to blockade the Strait of Hormuz following Israeli strikes on Iranian sites, Reuters reported on Wednesday, citing two US officials familiar with the matter.

The mine-loading activity, which had not been publicly disclosed earlier, took place shortly after Israel launched a missile attack on Iran on June 13. The US officials, speaking on condition of anonymity due to the sensitive nature of the intelligence, stated that the mines have not been deployed but their movement indicates serious Iranian consideration of blocking the strategic waterway.

The Strait of Hormuz is one of the world’s most vital shipping lanes, with nearly 20% of global oil and gas shipments passing through it. Any disruption could have sent global energy prices soaring. However, oil prices have fallen by more than 10% since US airstrikes on Iranian nuclear facilities, largely due to relief that shipping through the strait has remained unaffected.

Following US airstrikes on June 22 that targeted three key Iranian nuclear sites, Iran’s parliament reportedly supported a non-binding resolution to close the strait. However, the final decision rests with Iran’s Supreme National Security Council, as noted by Iran’s Press TV.

Historically, Iran has threatened to block the Strait of Hormuz during periods of heightened geopolitical tension but has never acted on those threats. Reuters reported that it remains unclear whether the mines remain aboard the Iranian vessels or if they have since been removed.

US intelligence gathering on the matter likely involved satellite imagery, human intelligence, or a combination of both, the sources added.