Dind Mohammad Darwesh, spokesman for the governor of Logar Province, said it was probably a case of militants killed by their own weapon.
He said it appeared the car was being prepared for a terror attack but that investigations are ongoing. He said today that those killed in the blast included nine insurgents, plus two women and two children who were nearby.
Darwesh had no further details. The area is a Taliban stronghold, and dangerous for journalists to independently verify claims.