An Iranian oil tanker pursued by the US has turned off its tracking beacon for over 13 hours.
The Adrian Darya 1, formerly known as the Grace 1, turned its Automatic Identification System off on Monday night. It has yet to be turned back on.
The move prompted renewed speculation that it is heading to Syria.
Previously, the ship-tracking website MarineTraffic.com showed the Adrian Darya off Lebanon on a course toward Tartus, Syria.
US Secretary of State Mike Pompeo claimed the ship would head to Tartus to offload its 2.1 million barrels of Iranian crude oil, worth some $130 million.
Iranian officials have not said where the ship would go, only that its cargo had been sold to an unnamed buyer.
The US Treasury Department on Friday blacklisted the tanker which was detained by Britain off Gibraltar in July due to British suspicion it was carrying Iranian oil to Syria in violation of European Union sanctions.
When the ship was released off Gibraltar in mid-August after a five-week standoff, Iran told Britain the cargo was not headed to Syria.
Iranian Foreign Minister Mohammad Javad Zarif accused the United States of engaging in “piracy and threats” to stop Tehran selling oil to traditional clients.