Newly released documents from the FBI reveal that there was a potential threat to assassinate Britain’s Queen Elizabeth II during her trip to the U.S. over 40 years ago.

The late Queen Elizabeth, Britain’s longest-reigning monarch, was scheduled to visit the U.S. with her husband, Prince Philip, in 1983. More than 100 pages of documents released by the FBI on Tuesday outline a serious threat made ahead of that trip and safety concerns that came up in other visits the queen made to the U.S.

The documents, which were posted publicly on the FBI’s website after a Freedom of Information Act request by NBC News, reveal that an unidentified San Francisco police officer received a tip about the potential plot to assassinate the queen on Feb. 4, 1983 — just a few weeks before the royal couple was scheduled to arrive in the U.S.

According to the documents, a man said that he was going to “attempt to harm Queen Elizabeth II,” and that he intended to try to kill her either while she was at Yosemite Park or “by dropping some object off the Golden Gate Bridge onto the Royal Yacht Britannia when it sails underneath.”

The documents didn’t include information on whether any arrests were made following the threat.

The man claimed that his daughter had been killed in Northern Ireland by a rubber bullet, according to the documents.

The 1983 trip to the U.S. occurred during a decadeslong period of sectarian conflict in Northern Ireland known as the Troubles. During this period, the unionists, most of whom were Protestants, wanted Northern Ireland to remain within the United Kingdom, while the nationalists, many of whom were Irish Catholics, and the Irish Republican Army wanted it to join the rest of Ireland.

The British deployed its military to Northern Ireland during the bloody conflict, which lasted for 30 years until a peace agreement was signed in 1998.

The FBI closely monitored the queen’s visits to the U.S. over the years with the help of the U.S. Secret Service, and security continued to be a concern.

“While [the FBI] is unaware of any specific threats against the Queen, the possibility of threat against the British monarchy is everpresent from the Irish Republican Army,” the FBI wrote in one document ahead of the queen’s 1989 visit to Kentucky.

During another visit in 1991, Irish groups organised protests at a baseball game and White House event where the queen was scheduled to appear, according to a document.

The FBI cited an article published in Irish Edition, a Philadelphia newspaper, that stated “anti-British feelings are running high” ahead of her trip.

The document added that while there were no threats against the queen or the president, who would also be attending the events, the statements “could be viewed as being inflammatory.”

Queen Elizabeth died in September at the age of 96; Prince Philip died in 2021 at 99.