The Interior Minister, Wais Ahmad Barmak confirmed the report, but he did not name the hospital which had owned the ambulance.
The ambulance packed with explosives was detonated in a crowded area of the city, close to Jamhoriat Hospital and High Peace Council buildings after passing through two checkpoints.
The death toll of the bombing has risen to 103 and 235 more wounded in the attack, Interior Minister Barmak said. The Taliban claimed responsibility for the attack.
Four suspects have been arrested in connection with the bombing, Barmak said.