Air safety investigators say a pressurized oxygen cylinder set off the blast that blew a large hole in the side of a Qantas jet last month, forcing an emergency landing.
The bombing followed a pattern of Taliban attacks against government security installations in retaliation for a fierce Pakistani campaign against Islamic militants.
Days of Christian-versus-Hindu retaliatory violence sparked by the killing of a Hindu leader has left at least 3,000 people, most of them Christians, homeless.