Taiwanese officials say there is no evidence terrorism or a missile caused a China Airlines jet to break up over the Taiwan Strait.
There has been speculation a bomb or a missile might have caused the crash on Saturday that killed 225 people.
Pilots did not send a distress signal before the Hong Kong-bound aircraft disappeared from radar screens 20 minutes after taking off from Taipei.
But the deputy director of the National Security Bureau, said his agency has investigated the theories and found no evidence to back them up.
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Taiwan's military has also said that it was not testing missiles or other weapons in the area when the plane crashed near the Penghu island chain, off Taiwan's western coast.
AP