GIBRALTAR (AP) — An Iranian supertanker hauling $130 million worth of light crude oil that the U.S. suspects to be tied to a sanctioned organization has lifted its anchor and begun moving away from Gibraltar, marine traffic monitoring data showed late Sunday.

The trail left by GPS data on Marinetraffic.com, a vessel tracking service, showed the Iran-flagged Adrian Darya 1, previously known as Grace 1, moving shortly before midnight. The tanker slowly steered southeast toward a narrow stretch of international waters separating Morocco and the southern tip of the Iberian Peninsula.

The vessel had been detained for a month in the British overseas territory for allegedly attempting to breach European Union sanctions on Syria. Gibraltar authorities rejected an eleventh-hour attempt by the United States’ to reseize the oil tanker on Sunday, arguing that EU regulations are less strict than U.S. sanctions on Iran.

The vessel’s next destination was not immediately known.

An on-duty officer at the Port Authority of Gibraltar declined to comment on the ship’s moves and deferred questions to the government. The Gibraltar government press office did not immediately respond to messages seeking comment.