An Iranian tanker captured by Royal Marines and detained by Gibraltarian authorities since July 4 was released late Sunday and sailed for Greece on Monday.

The final destination is unknown.

The Grace 1 tanker was carrying 2.1 million barrels of oil that the British government believes was initially bound to Syria, that is, a country that is under EU sanctions. Grace 1 is now renamed the Adrian Darya 1.

The US Department of Justice issued an injection on Sunday, attempting to prevent the release of the tanker. However, Gibraltar’s high court ruled that there was no legal grounds to keep the vessel in custody after Iran issued assurances that the cargo would not end up in Syria.

The US injunction was founded on the grounds that the tanker was allegedly linked to the Islamic Revolutionary Guards Corps (IRGC), which Washington has listed as a terrorist organization. The EU does not consider the IRGC a terrorist organization.

While the US has imposed an embargo on Iranian oil exports, the EU has not, although EU member states steer away from Iranian imports to avoid secondary sanctions. Therefore, no EU member state has legal grounds to detain the vessel.

The US Justice Department has issued a warrant for the supertanker’s seizure; on Monday, Tehran’s foreign ministry spokesman warned Washington against any unilateral action aiming to detain the vessel that is now believed to be bound for the port of Kalamata.

On Tuesday morning the Greek Maritime Affairs Ministry noted that “the vessel is cruising at low speed and there is still no formal announcement that it will arrive at Kalamata.”