official in japan are investigating two small explosions last night outside an american air base in tokyo. authorities believe they were caused by an improvised device. they found a timing mechanism at the scene and two tubes. carl penhall is live with the latest. i m sure the bomb squad is out there and investigators are trying to find out any evidence at all to figure out what happened here? reporter: jason a rosa, absolutely. the japanese police are taking this very seriously. we saw bomb squads 40 or 50 members, in fact, the bomb squad combing that area a few hundred yards from the perimeter of the u.s. air force base there and the police have confirmed they found two steel pipes connected to wires, connected to a battery and connected to a timing device. this was a homemade mortar