Two tankers carrying about 1 million barrels of Iranian crude oil have changed their destination signals to Karachi, in an unusual move that may suggest they are seeking a safe place to wait after the United States reimposed a naval blockade on Iranian shipping, Bloomberg reported.

According to ship-tracking data reviewed by Bloomberg, the vessels Rani and Amil altered their destination signals to Karachi on Tuesday after leaving the Persian Gulf. However, analysts said it is unlikely the tankers intend to unload their cargo in Pakistan, as such a move could expose the country to US sanctions. Pakistan has not officially imported Iranian crude oil for more than a decade, according to energy intelligence firm Kpler.

Industry experts said the vessels may instead anchor in Pakistani waters while waiting for further developments or transfer their cargo to other ships.

Similar patterns have been seen before, when Iran-linked tankers waited off Karachi during earlier periods of US sanctions before returning to the Persian Gulf.

Charlie Brown, an adviser to the nonprofit United Against Nuclear Iran, said remaining near Pakistan could offer operators a relatively secure location while they monitor developments, rather than signaling any intention to deliver Iranian oil to Pakistan. Xavier Tang, a senior market analyst at Vortexa, also suggested the vessels may be sailing closer to Pakistan to avoid US naval patrols and use Karachi as a waypoint.

Both tankers are sanctioned by the United States and are part of the so-called “dark fleet” used by Iran to transport crude oil. The development comes as Washington tightens enforcement of sanctions on Iranian oil exports amid renewed regional tensions.