"The number of remains that were exhumed so far is 47, and they were found in 11 mass graves," Kamel Amin told AFP, adding that the number is expected to rise.
Amin said they are believed to have been victims of the infamous Speicher massacre, named for the military base near which up to 1,700 mostly Shiite recruits were abducted by the Islamic State (IS) jihadist group last year.
But DNA testing is required to confirm their identity, he said.
The mass grave sites were discovered after Iraqi forces retook the city of Tikrit last week in their biggest victory so far against IS.
IS led an offensive last June that overran large areas north and west of Baghdad, but Iraqi security forces and allied paramilitaries have succeeded in regaining significant ground.