The US Department of Justice has made a last-minute request to the authorities in Gibraltar to halt the release of a seized Iranian supertanker. Grace 1, carrying Iranian oil, was stopped by Royal Marines on 4 July, triggering a standoff with Tehran. The vessel was due to be released, after Gibraltar's attorney general indicated there would be no further order for its detention. But the US request will be considered, with a court hearing set for 15:00 BST. Gibraltar said the US application is based on a "number of allegations which are now being considered". The UK Foreign Office said it was unable to comment on the US request. A spokesman for Gibraltar's government also confirmed that police proceedings against four members of the crew, including the captain - an Indian national - had ended. The crew's legal team told the BBC that police had said this was due to actions by the Iranian government, and that it was no longer in the public interest to proceed. The crew of 28 are Indian, Russian, Latvian and Filipino and have spent 43 days in detention on board the ship. The Grace 1's captain said in a statement: "I am grateful and thankful for my release. And I am grateful to all who have facilitated my release in my legal team." The tanker was seized after the government of Gibraltar suggested it was heading for Syria, in breach of EU sanctions. About 30 marines were flown from the UK to Gibraltar to help police detain Grace 1 and its cargo, at the request of the Gibraltar government. The initial seizure of the tanker sparked a diplomatic crisis between the UK and Iran, which has escalated over recent weeks and saw the seizure of a British-flagged and Swedish-owned oil tanker, Stena Impero, in the Gulf. The Gibraltar authorities have since received assurances from the captain of the ship and Iran that Grace 1 would not travel to Syria.