A British newspaper received a mystery tip-off about “some big news” in the U.S., minutes before President John F. Kennedy was assassinated, according to newly released documents.

A memo to the director of the FBI revealed that an anonymous phone call was made to an unnamed senior reporter at Cambridge News on the day Kennedy was shot in Dallas, Texas, in 1963 is among those that has been released among a tranche of new archive documents released Thursday.

“The British Security Service (MI-5) has reported that at 1805GMT on 22 November an anonymous telephone call was made in Cambridge, England, to the senior reporter of the Cambridge News,” read the note, which was sent by CIA deputy director James Angleton.

“The caller said only that the Cambridge News reporter should call the American Embassy in London for some big news and then hung up.

“After the word of the president’s death was received the reporter informed the Cambridge police of the anonymous call and the police informed MI-5.”

According to the document, which was dated four days after the assassination, MI-5 calculated that the call was made about 25 minutes before Kennedy was shot.

“The Cambridge reporter had never received a call of this kind before and MI-5 state that he is known to them as a sound and loyal person with no security record,” added the memo.

The document was made public in a collection of nearly 3,000 declassified files relating to Kennedy’s murder that was released Thursday at the order of President Donald J. Trump.

The release of many files will be held back for a further 180 days, however, after intelligence agencies requested more time to redact information that could cause “potentially irreversible harm”.

Current staff at the Cambridge News said there were no records on who took the call, but they were speaking to people who worked there in the 1960s to find out, according to the Daily Mail.

Anna Savva, a reporter at the newspaper, described learning about the phone call as “completely jaw-dropping”.

She said: “It would have been common knowledge in the office who took the call, but we have nothing in our archive – we have nobody here who knows the name of the person who took the call.”