A regional judge said in court papers released today that at least 31 bodies found in a mass grave about 15 miles from here belong to people who were likely killed in battles with Argentine security forces.

In a document asking federal courts to take charge of an investigation of the identities of the 400 bodies buried at the Grand Bourg cemetery, Judge Hugo Gandara cited 31 notations in the grave registry listing causes of death as "military confrontation" and "army battle" next to the names.

It was the first time a government official has linked such a large number of bodies with the "dirty war" fought between Argentine security forces and two leftist guerrilla organizations between 1974 and 1979. Between 6,000 and 15,000 persons vanished in Argentina during that time, human rights activists and others charge.

One foreign observer characterized the revelation as a "political bombshell."

Human rights groups have linked many of the disappearances to government security forces, but the generals who have ruled this country since taking power in a coup in 1976 have denied specific knowledge of the missing persons' whereabouts.

Gandara's investigation began Friday when six parents of missing people asked him to impound all records and documents relevant to burials at the cemetery, which was opened in 1976. The graveyard is less than one mile from the Campo de Mayo Army installation, Argentina's biggest such facility.

Citing testiony from graveyard workers and neigbors, the petition alleges that nighttime burial of bodies by Argentine security forces as well as the recent discovery there of the body of a labor organizer missing since 1976 pointed to the strong possibility of other missing people being interred at the cemetery.

It was revealed yesterday that Gandara had decided to remove himself from the case because of the involvement of security forces.