Updated at 2 p.m. to clarify the number of documents remaining under seal.

WASHINGTON — President Donald Trump issued an order Thursday, keeping some of the most sensitive records from the Kennedy assassination files sealed for another 3 1/2 years, as the National Archives released a final batch under a law meant to force most of the records into the light by last fall.

In 1992, Congress set a 25-year deadline for releasing remaining documents stemming from John F. Kennedy's murder in Dallas on Nov. 22, 1963.

When the deadline arrived — Oct. 26 last year — Trump gave federal agencies a six-month extension to plead the case for keeping selected records sealed, if they could assert a vital national security interest. The FBI and CIA in particular had pressed for more time.

Some 15,884 records that have now been partially released, some with heavy redactions, will be subject to yet more review over the next three years under Trump's order.

The National Archives released 19,045 documents Thursday. Those can be downloaded here, along with previously released records, such as secret 1978 testimony from a former CIA station chief in Mexico City, David Atlee Phillips, a Fort Worth native.

He called assassin Lee Harvey Oswald "loony" and insisted that as far as he could tell, Oswald had acted alone.

"God knows I would like for it to come out that Fidel Castro was responsible or that the Soviets were responsible," Phillips testified before the House Select Committee on Assassinations, under questioning by Rep. Floyd Fithian, an Indiana Democrat. "But I know of no evidence to show that the Cubans or the Soviets put him up to it, and I just have to go along on the side that he was a kind of loony fellow who decided to shoot the president, and he did."

The transcript of the four decade-old testimony was in the batch of documents released Dec. 15. Historians, assassination buffs and conspiracy theorists are still digging through those and other previously secret files for insights into the investigation and countless unrelated topics, from the U.S. escalation in Vietnam to assassination plots and meddling with unfriendly regimes in Cuba, Chile and other nations.

(Hat tip to Bud Kennedy of the Fort Worth Star-Telegram for flagging the Phillips testimony.)

19,045 documents subject to the President John F. Kennedy Assassination Records Collection Act of 1992 have been posted on @USNatArchives website. Released documents are available for download: https://t.co/E5lR7OzeWI — US National Archives (@USNatArchives) April 26, 2018

According to the National Archives, 520 documents remain under seal under one of two provisions of the 1992 law. Some were sealed by a federal court and can only be unsealed by a judge. Others involve tax records. Of the 15,834 released only in redacted form, "most are currently less redacted than prior to October 26, 2017."

Some of the newest documents have only the Social Security number of a witness blacked out, for instance.

Much of the latest release involves organized crime case apparently unrelated to the JFK killing or investigation.

Since last July, the archives has released 13,371 documents in full.

In a presidential memorandum Thursday, Trump wrote that the Archivist of the United States had, over the last 180 days, reviewed records that remained sealed in the collection that agencies had sought to keep sealed or redacted "because of identifiable national security, law enforcement, and foreign affairs concerns. The Archivist has reviewed the information agencies proposed to withhold and believes the proposals are consistent with the standard of section 5(g)(2)(D) of the President John F. Kennedy Assassination Records Collection Act of 1992. ...

"I agree with the Archivist's recommendation that the continued withholdings are necessary to protect against identifiable harm to national security, law enforcement, or foreign affairs that is of such gravity that it outweighs the public interest in immediate disclosure."

"I am also ordering agencies to re-review each of those redactions over the next 3 years," and to immediately release records that no long warrant ongoing withholding, Trump wrote.

The president signaled a willingness to allow some records to remain sealed beyond Oct. 26, 2021.

But, citing the 1992 law, he added, " 'only in the rarest cases is there any legitimate need for continued protection of such records.' The need for continued protection can only grow weaker with the passage of time."

Records released in the last year included FBI and CIA reports on Soviet spies, the assassination of the Rev. Martin Luther King Jr., and Lee Harvey Oswald's trip to Mexico City a few weeks before he murdered Kennedy.

For decades, debate has raged not only over whether Oswald acted alone but also whether the FBI and CIA could have stopped him. The voluminous record shows unequivocally that he was in their sights, though none of the records unsealed in the last year has fully put to rest conspiracy theories.

For instance, a 1975 CIA memo marked "top secret" shows that Oswald was on a "watch list" of people whose mail would be intercepted from Nov. 9, 1959, to May 3, 1960, and again from Aug. 7, 1961, through May 28, 1962.

The Phillips testimony from 1978, released Dec. 15, counts on the Oswald acted alone side of the ledger.

"The American public doesn't want to believe that one man could murder Camelot," he told House investigators.