The U.S. has filed a warrant to seize all oil aboard an Iranian oil tanker impounded in Gibraltar last month as well as nearly $1 million, according to federal court documents unsealed on Friday.

The seizure warrant and forfeiture complaint is based on the International Emergency Economic Powers Act as well as other statutes that deal with money laundering, bank fraud and a terrorism forfeiture statute, the Department of Justice said.

The tanker, Grace 1, was detained last month in a British Royal Navy operation off of Gibraltar, and it was suspected of violating European Union sanctions on oil shipments to Syria, which is an ally of Iran.

Gibraltar officials had said this week that the U.S. Department of Justice had applied to seize the Grace 1.

While the U.S. announced it obtained the warrant to seize the tanker, Gibraltar court officials said they had not received any claim by the end of the business day, and it was not clear whether the U.S. had forwarded it, the Associated Press reported.

The U.S. government claims in the court documents that the Grace 1, which is capable of carrying more than 2 million barrels of crude oil, is part of a scheme to support illicit shipments from Iran by that country’s Revolutionary Guard Corps. President Donald Trump has designated the guard corps as a foreign terrorist organization.

The U.S. says that the oil tanker engaged in "deceptive voyages" from Iran to other locations, including Syria.

"The scheme involves multiple parties affiliated with the IRGC and furthered by the deceptive voyages of the Grace 1. A network of front companies allegedly laundered millions of dollars in support of such shipments," the Justice Department said in a statement, referring to the Revolutionary Guard Corps.

On Thursday, Gibraltar's government confirmed that the oil tanker has been released from legal detention. The tanker shifted its position on Friday, but its anchor was still down off Gibraltar and it was unclear if it was ready to set sail soon, Reuters reported. Gibraltar is an overseas British territory.

Gibraltar's chief minister, Fabian Picardo, has said that he received assurances from Iran that the tanker would not head to an entity that is subject to E.U. sanctions. A Gibraltar government spokesperson said that Iran has provided commitments, but also that evidence located aboard the Grace 1 "demonstrates that the vessel was going to Syria."

The U.S. court documents allege that before the tanker was seized by British authorities, "a confidential source revealed that the Grace I was scheduled to arrive in Syria in early July."

The documents claim that charts and electronic equipment on board show the tanker was destined for a port in Syria, which would be in violation of U.S. sanctions.

The seizure of Grace 1, which occurred on July 4, became a simmering point in the ongoing tensions between Iran and the west.

Weeks after the tanker was seized by British authorities, Iran seized a British oil tanker, the Stena Impero, in the Strait of Hormuz.

Iran's ambassador to the U.K. has called the seizure and detention of the Grace 1 an illegal act. Iran's foreign minister, Mohammad Javad Zarif, tweeted on Thursday that "detention was 100% unlawful."

In addition to the tanker and the oil aboard, the U.S. is seeking to seize $999,950 that it says is at a U.S. bank which was not named, according to the unsealed court documents.