A Pentagon review has concluded that sensitive encoded circuit boards that disappeared after a failed launching of an American communications satellite in China two years ago were most likely destroyed in the fiery crash.

Last month Defense Department officials said they suspected that Chinese authorities had stolen the devices from the wreckage of a $200 million satellite that was obliterated when the Chinese rocket carrying it exploded shortly after it took off.But a review by the National Security Agency, the military's supersecret code-makers and codebreakers, found no evidence of Chinese wrongdoing.

"It is highly unlikely that the devices survived the crash because of the crash impact and high temperatures produced by burning rocket propellants," said the review, which noted that the devices were housed very close to the rocket's fuel tank.

In the off-chance that the Chinese recovered the chips, which tell an orbiting satellite which way to point in order to receive and transmit signals, they would not have learned much, the review concluded: "It is highly unlikely that these items could have been recovered in sufficient detail" to enable the Chinese to reproduce them.

The White House ordered the review after House Republicans voiced fears at a hearing last month that the loss of the encoded circuit boards might have harmed national security.

The case of the missing circuit boards became part of a congressional inquiry into whether sensitive American satellite technology was given to China that ultimately may enhance Beijing's military.

After the House hearing last month, the White House issued a statement from the National Security Agency that said the loss of the devices would have "minimal" impact on American security because the technology was 20 years old.