The ship is now anchored in the Gulf of Oman, the Associated Press reported, but no information about its crew is known. Newsweek previously reported that the tanker’s crew was not injured in the October 24 seizure.

However, according to a spokesperson for the Iranian United Nations mission, the ship did not leave the port with its original batch of oil.

“Sothys left Iranian waters last night after transferring the oil,” spokesperson Shahrokh Nazemi told AP. Iranian state media reported that the oil was drained from the Sothys under a court order, but no other information was given.

The seizure of the Sothys is the latest in a string of hijackings in the Gulf of Oman, where one-fifth of all oil traded in the world passes. The U.S. Navy has accused Iran of numerous naval attacks, including a drone attack that killed two European crew members this year. Iran has denied any involvement in the attacks.

Vietnamese officials, who are still trying to obtain information about the seizure, could not be reached for comment, while the U.S. Navy 5th Fleet declined comment.

For more reporting from the Associated Press, see below.

The release of the Sothys ended the latest maritime confrontation involving Tehran amid stalled negotiations over its tattered nuclear deal with world powers.

Iran’s powerful paramilitary Revolutionary Guard troops on October 24 took control of the MV Sothys, a vessel that analysts suspect of trying to transfer sanctioned Iranian crude oil to Asia. U.S. forces had monitored the seizure but ultimately didn’t take action as the vessel sailed into Iranian waters.

Iran later celebrated its capture of the vessel in dramatic footage aired on state television, the day before the 42nd anniversary of the 1979 seizure of the U.S. Embassy in Tehran.

The Sothys had been on the radar of United Against a Nuclear Iran, a New York-based advocacy group long suspicious of the Islamic Republic. In a letter dated October 11 addressed to the Vietnam Maritime Administration, the group said its analysis of satellite photos showed the Sothys received a ship-to-ship transfer of oil in June from an oil tanker called the Oman Pride.

The U.S. Treasury identified the Oman Pride in August as being used to transport Iranian oil as part of a smuggling scheme to enrich the Guard’s expeditionary Quds Force. That Iranian oil ends up being sold into East Asia, the Treasury alleged, without identifying a specific country.

Just a few months ago, Iranian hijackers stormed and briefly captured a Panama-flagged asphalt tanker off the United Arab Emirates.

Tehran denies carrying out the attacks, but a wider shadow war between Iran and the West has played out in the region’s volatile waters since then-President Donald Trump withdrew the U.S. from Iran’s nuclear deal in 2018 and imposed crushing sanctions on the country.