Wahid Sediqqi, spokesman for the Parwan governor, on Monday said that the Bagram Airbase suicide bomber had been working on the base.
The bomber detonated his explosives early Friday, killing four and wounding more than 17.
The base is one of the most secure facilities in Afghanistan.
The suicide attacker, named Enayatollah, lived in Bagram, and had previously been a Taliban member. He joined the peace process four years ago, said Sediqqi.
Enayatollah had worked at the base for four years but had been persuaded to carry out the attack by the Taliban, said Sediqqi.