Just a few weeks before killing President John F. Kennedy in November 1963, Lee Harvey Oswald traveled to Mexico City, where he spoke with a KGB officer at the Soviet Embassy, a new document released Wednesday details. 

Nearly 1,500 documents related to the investigation into President Kennedy’s assassination were released to the public by the National Archives on Wednesday, the second major batch of assasination documents to be released since 2017. 

Among the documents are notes about a call Oswald made to the Soviet Embassy in Mexico City on October 1, 1963, on which the CIA was secretly listening. 

The CIA report says the agency learned via this call that Oswald went to the Soviet Embassy in Mexico City a few days prior, on September 26, where he met with Consul Valery Vladimirovich Kostikov. Kostikov, the CIA notes in the document, was an “identified KGB” officer involved with a branch of the secret service responsible for “sabotage and assasination.”

During the call, Oswald spoke to a guard and asked whether there was “anything new concerning the telegram to Washington.” 

“The guard checked and then told Oswald that the request had been sent but nothing new received,” the CIA notes on the call revealed. 

The CIA report noted that the FBI had reason to believe Oswald’s visit to the Soviet Embassy was to get support on a “US passport or visa matter.” 

The CIA official who wrote the memo also appeared skeptical that Oswald would have showed up to the Soviet Embassy if he were a KGB spy. 

“Of course it is not usual for a KGB agent on a sensitive mission to have such overt contact with a Soviety Embassy. However, we have top secret Soviety intelligence documents, describing Military Intelligence doctrine, which show that very important agents can be met in official installations using a cover for their presence there,” the report said. 

After Kennedy was killed, Mexican authorities arrested a Mexican employee of the Cuban embassy with whom Oswald had communicated, and she said Oswald had “professed to be a communist and an admirer of Castro”, according to the cable.

Another document weighs whether Oswald, while living in New Orleans, might have been affected in any way by the publication in the local newspaper of an interview an Associated Press correspondent conducted with Castro in which Castro warned of retribution if the US were to take out Cuban leaders.

The new files include several FBI reports on the bureau’s efforts to investigate and surveil major mafia figures like Santo Trafficante Jr and Sam Giancana, who are often mentioned in conspiracy theories about Kennedy’s assassination.

Apart from the Kennedy investigation, some of the material will be of interest to scholars or anyone interested in the minutiae of 1960s counterespionage, with pages and pages of arcane details on such things as the methods, equipment and personnel used to surveil the Cuban and Soviet embassies in Mexico City.

In blocking the release of hundreds of records in 2017 because of concerns from the FBI and the CIA, Donald Trump cited “potentially irreversible harm”. Even so, about 2,800 other records were released at that time.

The Warren commission in 1964 concluded that Oswald had been the lone gunman, and another congressional investigation in 1979 found no evidence to support the theory that the CIA had been involved. But other interpretations have persisted.