Helms, chairman of the Senate Foreign Relations Committee, said there is ``substantial and growing evidence'' that U.S. military and civilian authorities were aware that the civilian aircraft were in danger before the MiGs shot them down.
``U.S. officials watched on radar as Cuban MiGs headed towards the civilian aircraft, and in one instance, we know that a U.S. Customs official alerted Tyndall Air Force Base in Florida,'' Helms said.
Helms, R-N.C., sent identical letters to Defense Secretary William Perry, Secretary of State Warren Christopher and Treasury Secretary Robert Rubin.
He asked that the inspectors general of each agency conduct an investigation.
The House International Relations subcommittee on the Western Hemisphere voted last month to subpoena U.S. military and customs officials with knowledge of the incident.
© Copyright 1996 The Associated Press