Allegations that Lee Harvey Oswald was connected to the US Central Intelligence Agency (CIA) were "totally unfounded", say newly released documents regarding president John F Kennedy's assassination.
A 1975 CIA memo says a thorough search of agency records in and outside the United States was conducted to determine whether Oswald had been used by the agency or connected with it in "any conceivable way".
The memo said the search came up empty. The memo also said there was also no indication that any other US agency used Oswald as a source or for recruitment.
The US National Archives released another 676 government documents related to the assassination - the third public release so far this year. Under law, all the documents were to be disclosed to the public last week.
Most of the latest release comprises 553 records from the CIA that previously were withheld in their entirety.
There also are records from the US Justice and Defence departments, the US House of Representatives' Select Committee on Assassinations and the National Archives.
University of Virginia historian Larry Sabato complained that many of the documents in the latest release were still heavily redacted.
He tweeted about a 144-page record, titled "Material Reviewed at CIA headquarters by House Select Committee on Assassinations staff members," that had writing on only a handful of pages.
President Donald Trump has ordered the release of all records related to the assassination, and they are expected to be made public on a rolling basis during the next three to four weeks.
He also directed agencies to take another look at redactions and withhold information only in the rarest of circumstances.
One record showed how US officials scrambled after the assassination to round up information about Oswald's trip to Mexico City weeks earlier.
Officials wondered whether Oswald had been trying to get visas at the Soviet and Cuban embassies in Mexico City in order to "make a quick escape after assassinating the president".
A CIA message sent November 24 1963 - two days after Kennedy was killed - said an "important question" that remained unsolved was whether Oswald had been planning to travel right away or return to the US and leave later.
Another record dated April 11 1964, recounted a visit to the CIA by three staff members of the Warren Commission, which was set up to investigate the assassination.
The memo said the staff members indicated that Thomas Mann, former ambassador to Mexico and then-assistant secretary for inter-American affairs, "still has the 'feeling in his guts' that (Cuban leader Fidel) Castro hired Oswald to kill Kennedy".
They said, however, that the commission has not been able to get any proof of that.