The Soviet Union initially denied knowledge of the incident, but later admitted the shootdown, claiming that the aircraft was on a spy mission. The Politburo said it was a deliberate provocation by the United States to test the Soviet Union's military preparedness, or even to provoke a war. The United States accused the Soviet Union of obstructing search and rescue operations. The Soviet military suppressed evidence sought by the International Civil Aviation Organization (ICAO) investigation, notably the flight data recorders, which were eventually released eight years later after the collapse of the Soviet Union.