The site, the second-largest such site found in Bosnia since the end of the war, contains the bodies of Muslims and Croats slain at two wartime concentration camps.
"So far we have exhumed 415 bodies," Esad Bajramovic of the Commission for Missing People said.
Bajramovic added that the exhumation work which started at the end of August is to continue for at least two more weeks, with dozens more bodies expected to be found.
The bodies of inmates at the notorious Omarska and Keraterm camps were initially buried somewhere else and had been moved to the mass grave in the village of Kevljani, just outside the north-western town of Prijedor.
Thousands of non-Serbs were held in the camps in the Prijedor region.
Images of emaciated prisoners from those camps shocked the world when they were first broadcast in the summer of 1992.
About 18,000 bodies have been exhumed from more than 300 mass graves throughout the country, most of them Muslims, according to forensic teams.
Exhumation work is to continue
for at least two more weeks
About 16,000 people, including 3200 from the Prijedor area, are still listed as missing.
Bosnia's war claimed more than 200,000 lives and spawned 2.2 million refugees, more than half the Balkan country's population.
The conflict pitted Bosnia's Muslims, Croats and Serbs against each other.