BUENOS AIRES – U.S. Ambassador Noah Mamet handed over to Argentine officials 500 newly declassified files related to the “dirty war” against dissidents waged by the military regime that ruled the South American country between 1976 and 1983.

The documents “are of great interest” since they include testimony from victims and reports from US diplomats and intelligence agencies, Human Rights Secretary Claudio Avruj told EFE.

“These reports may reveal new facts or support facts that until now were hypothetical, so we are anxious to be given authorization to disclose them publicly,” Avruj said.

The files, dating from 1975 to 1983, span all or parts of the administrations of Presidents Richard Nixon, Gerald Ford, Jimmy Carter and Ronald Reagan, the official said.

The documents were delivered at the National Memorial Archive during a ceremony in honor of the late Patricia Derian, a civil rights activist who served as US Assistant Secretary of State for Human Rights and Humanitarian Affairs from 1977 to 1981 under Carter.

Derian, who died in May at the age of 86, was an outspoken critic of the crimes of the military regime and in 2006 received the Order of the Liberator Gen. San Martin, the highest decoration granted by Argentina to foreign officials.

Derian’s “work in 1977 led to a visit to Argentina in 1979 by the Inter-American Human Rights Commission, which was followed by the disclosure of material which was known to few people then, and which most people couldn’t even believe,” Avruj said.

During a visit to Buenos Aires in August, U.S. Secretary of State John Kerry delivered a first batch of declassified documents to Argentine President Mauricio Macri.

The handover of all relevant material is expected to be completed next year.

The 1976-1983 junta is blamed for some 30,000 deaths.