The JFK Assassination Files: What's In Newly Released Documents?

WASHINGTON (CBS/AP) — Newly released files in the assassination of President John F. Kennedy say then-FBI Director J. Edgar Hoover was focused on minimizing conspiracy theories immediately following the JFK assassination.

"The thing I am concerned about, and so is (deputy attorney general) Mr. Katzenbach, is having something issued so we can convince the public that Oswald is the real assassin," Hoover said an hour after Oswald was killed, according to CBS News.

Read: 3 Tips For Reading JFK Assassination Files

The batch of 2,800 declassified documents released late Thursday includes a memo to the director of the FBI, dated November 26, 1963, that details how a British newspaper received an anonymous call about "big news" in the United States minutes before Kennedy on November 22.

It says the caller said that "the Cambridge News reporter should call the American Embassy in London for some big news, and then hung up."

The memo says Britain's MI5 intelligence service calculated that the call came 25 minutes before Kennedy was shot in Dallas.

Anna Savva, a current Cambridge News reporter, says the paper has no record of who took the call. She said Friday that learning of the call was "completely jaw-dropping."

CBS News has had a team of investigators combing through the papers released online by the National Archives.

Here's a sampling of what they have found:

Interview with Former Assistant Director of FBI, James H. Gale: "…Oswald might have ha foreign intelligence connections – Soviet or Cuban – although none was ever found…no knowledge that Oswald was ever an FBI informant."

Secret Service threat list: This 413-page memo lists every threat the Secret Service was watching between March and December 1963, including KKK Klansmen, Puerto Rican Nationalists, gang members, and individuals with a history of mental illness. Included is a brief description indicating their history and degree of threat.

FBI memo discusses Oswald prior to JFK assassination: On November 25, 1963, a memo showed that the FBI had been keeping tabs on a Pro-Castro "Fair Play for Cuba Committee," what Oswald was a part of.

Read: CBS News Live Updates On JFK Files

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)