Former Major Ernesto "Nabo" Barreiro, who is on trial for crimes against humanity, gave the court a list of some two dozen people he said had been buried inside two large earthen ovens at a military base outside the central city of Cordoba.
Judge Jaime Diaz Gravier said it was the first time a former officer had broken the code of silence around the regime's so-called "Dirty War" against leftist opponents since the South American country's return to democracy.
According to survivors, Barreiro was in charge of prisoner interrogations at a secret detention camp known as "La Perla" (the pearl) that operated at the base.
He is accused of some 400 counts of crimes against humanity, and is standing trial with three co-defendants.
He told the court that "20 or 21 disappeared" had been buried in one oven at the base, a site where forensics experts found human remains in October.
That site could not immediately be located.
"The search will continue with the appropriate technology," said the judge.
A lawyer representing victims' families cast doubt on Barreiro's revelation.
"A ton of families with a lot of anguish and expectations were following this and suffered a new let-down. It delivered absolutely nothing," said the lawyer, Claudio Orosz.
Barreiro is known in Argentina as the man at the center of a 1987 military uprising against then-president Raul Alfonsin's government that demanded an amnesty for dictatorship-era crimes.
An estimated 30,000 people were killed or abducted and presumed killed during the dictatorship.
