Trump blocks release of some JFK assassination files

Some records were withheld due to national security concerns, according to a memo from President Trump, while more than 2,800 previously classified or redacted records were released by the National Archives.
4:42 | 10/27/17

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Transcript for Trump blocks release of some JFK assassination files
First new details revealed in the top secret JFK files, thousands about the Kennedy assassination becoming public but some blocked by president trump for national security reasons. Our chief national correspondent Tom llamas is at the national archives in Washington with all of those details. Good morning, Tom. Reporter: Amy, good morning to you. This is just a sample of some of those documents. Everything from FBI interrogation memos to receipts to the actual CIA plans to kill Fidel Castro with poison pills. There's so much information here and our team spent all night going through those 2,800 documents but as you mentioned some remain secret but still there is so much material in these documents for people who like conspiracy theories to cherry-pick and build their case. This morning, thousands of documents shedding new light on the investigation into the assassination of JFK but also adding to the mystery of what happened in dealey plaza on November 22nd, 1963. The newly released files show an effort by investigators to chase down every lead. This FBI memo from 1964 disputing claims assassin Lee Harvey Oswald was an FBI informant, finding he was never paid money or ever assigned an official symbol number like a code name. . There is Lee Harvey Oswald. He's been shot. Reporter: On the day Oswald was shot and killed two days after Kennedy this memo from the head of the FBI apparently. J. Edgar Hoover demanding public doubt be dealt with saying he wants something issued so that we can convince the public that Oswald is the real assassin. Assassins need payroll, schedules, times, orders. This was a military-style ambush from start to finish. This was a coup d'etat with Lyndon Johnson waiting in the wings. Reporter: The film "JFK" and its fictional plot to kill Kennedy fueling more speculation and in part leading to the assassination records collection act of 1992 which required all federal assassination records be released before today. What experts want to know is if the documents, some still secret, will show Oswald was being tracked in Mexico City seven weeks before the assassination and mentioned his plan. Was the middle of the cold war and we could find out if they heard Oswald say something that was threatening against the president and if they did what did they do about it. Reporter: But the biggest secrets remain so far a mystery, the FBI and CIA appealing to the white house to not release documents with sensitive information. Why? A danger to national security. The CIA saying in part, they needed to protect information including the names of current and former CIA officers, and specific intelligence methods that remain viable to protecting the nation today. Now, as for those secret documents that still remain behind closed doors at the national archives president trump has ordered a review of those to see if at some point in the next 180 days they can be released to the public. Amy. And, Tom, as you mentioned you and your team have been poring over these documents throughout the night. Does anything stand out to you? Reporter: You know, Amy, reading through these hundreds of documents, thousand, there is a running theme that investigators really tried to chase down every lead. We saw one memo where the secret service chased down a dollar bill that had a threat written to the president on it in 1964. This was just a random dollar bill that was in circulation and then a memo from 1976 from the CIA outlining a new policy that they were no longer going to enter into paid contracts with American clergymen like priests but also, Amy, news correspondents. Oh, that is interesting. Tom, George here. Another thing, in six months we're likely to see several more thousand documents come out after the review, some will probably be held back but the conspiracy theories will never go away because so many other documents are missing or destroyed. Reporter: That's so true, George. Even with the ones they released, there's so many new nuggets and new names and so much information, now open widely to the public and really it's such an interesting read I invite all of our viewers to logon to the archives website. It is a fascinating read and reads like a spy thriller novel and, again, it was on one of the darkest days in American history, George. Incredible stuff. Tom, thank you very much. The mystery continues. And it will.

This transcript has been automatically generated and may not be 100% accurate.

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