Forensics tests suggest that an explosion was responsible for the crash of a Romanian plane shortly after it took off from Bucharest and headed for Brussels last Friday . All 59 people onboard were killed. Witnesses had described seeing Tarom airline's Airbus A310 explode in mid-air. The Bucharest airport received another bomb threat today when an anononymous caller claimed that explosives had been placed on a flight bound for Paris. The plane was grounded, but no bomb was found.