Updated at 12:55 p.m. ET
Gibraltar has released an Iranian oil tanker that was detained last month by Britain, despite a last-minute request by the U.S. to take possession of the vessel.
Grace 1 was raided on July 4 in the waters off the coast of Gibraltar, a British territory, by Britain's Royal Marines. The tanker was impounded on suspicion of transporting oil to Syria — a breach of European Union sanctions against Syrian President Bashar Assad's regime. It was said to be carrying 2.1 million barrels of crude oil.
Gibraltar's Chief Minister Fabian Picardo confirmed those suspicions on Thursday, but said in a statement that he had received "written assurance" from Iran that the tanker would not head to Syria with its cargo.
"In light of the assurances we have received, there are no longer any reasonable grounds for the continued legal detention of the Grace 1 in order to ensure compliance with the EU Sanctions Regulation," Picardo said.
The tanker's release from detention was decided Thursday afternoon local time by the Gibraltar Supreme Court.
A spokesperson with Gibraltar's government told NPR on Thursday that the Justice Department had applied to seize the vessel, providing "a number of allegations which are now being considered."
The U.S. Department of Justice did not immediately respond to NPR's request for comment.
Mohammad Javad Zarif, Iran's foreign minister, took to Twitter after the news of the release.
"The US attempted to abuse the legal system to steal our property on the high seas," he wrote. "This piracy attempt is indicative of Trump admin's contempt for the law."
According to a legal notice provided Thursday by the Gibraltar government, the Grace 1's passage plan plotted 38 specific waypoints for a route from the Persian Gulf to Baniyas, where a major oil refinery is located in northwestern Syria.
"There were no plotted navigational charts, passage plans, plotted courses or underkeel clearance calculations on board the Vessel relating to a destination other than Syria," the notice said.
Emails from April to July between the captain and managing agents showed permit requests and a directive to land the ship's waste at the discharge port — deemed to be Syria. The government of Gibraltar said it confirmed that the vessel was the property of the state-owned National Iranian Oil Company.
Days after the tanker was taken, Iran's Revolutionary Guard seized a British-flagged commercial oil tanker, called the Stena Impero, in the Strait of Hormuz — a vital shipping route linking the Middle East to the world. Iran also briefly detained a U.K.-owned oil tanker, Mesdar.
On Wednesday, Iranian Navy Commander Rear Admiral Hossein Khanzadi was quoted by Iran's Press TV with a warning that enemies should leave the region. "The era of hypocritical stunts and roaming freely around in the Persian Gulf is over," he said.
The seizures this summer have escalated relations between the West and Tehran. Tensions had already run high since President Trump's withdrawal last from the 2015 Iran nuclear deal.
Under the agreement, Iran said it would curb its nuclear programs in exchange for the U.S. easing of sanctions. The Trump administration has since imposed new economic sanctions on Iran, and Iran said it has begun to enrich uranium above the levels established in the agreement.