An Iranian supertanker with $130 million worth of light crude oil that the U.S. suspects is tied to a sanctioned organization has left Gibraltar and is heading east into the Mediterranean Sea, with its next destination reported to be Greece.

Ship tracking service MarineTraffic said on Monday that the Iran-flagged Adrian Darya 1, previously named Grace 1, has set course for Kalamata, Greece, with an estimated arrival on Aug. 25. It wasn't immediately clear why the tanker would be heading there or whether the destination could change.

The vessel left Gibraltar late on Sunday after having been detained for a month in the British overseas territory for allegedly attempting to breach European Union sanctions on Syria. Gibraltar authorities rejected attempts by the U.S. to seize the oil tanker.

Renamed Adrian Aryra 1 super tanker hosting an Iranian flag, sails in the British territory of Gibraltar, Sunday, Aug. 18, 2019. Authorities in Gibraltar on Sunday rejected the United States' latest request not to release a seized Iranian supertanker, clearing the way for the vessel to set sail after being detained last month for allegedly attempting to breach European Union sanctions on Syria. (AP PhotoMarcos Moreno)

Renamed Adrian Aryra 1 super tanker hosting an Iranian flag, sails in the British territory of Gibraltar, Sunday, Aug. 18, 2019. Authorities in Gibraltar on Sunday rejected the United States' latest request not to release a seized Iranian supertanker, clearing the way for the vessel to set sail after being detained last month for allegedly attempting to breach European Union sanctions on Syria. (AP PhotoMarcos Moreno)

A supertanker hosting an Iranian flag is seen on the water in the British territory of Gibraltar, Sunday, Aug. 18, 2019. Authorities in Gibraltar on Sunday rejected the United States' latest request not to release a seized Iranian supertanker, clearing the way for the vessel to set sail after being detained last month for allegedly attempting to breach European Union sanctions on Syria. (AP PhotoMarcos Moreno)

A supertanker hosting an Iranian flag is seen on the water in the British territory of Gibraltar, Sunday, Aug. 18, 2019. Authorities in Gibraltar on Sunday rejected the United States' latest request not to release a seized Iranian supertanker, clearing the way for the vessel to set sail after being detained last month for allegedly attempting to breach European Union sanctions on Syria. (AP PhotoMarcos Moreno)