KIEV, Ukraine –– The Ukrainian Defense Ministry denied Thursday any of its forces fired a rocket which could have hit the Russian aircraft that exploded and crashed into the Black Sea. 

A senior U.S. military official in Washington said the plane may have been downed by a surface-to-air missile fired during a military exercise in Ukraine. Russian officials were investigating the possibility of a terrorist attack. 

All the rockets used in the training exercise have "self-destruction mechanisms in case they deviated from their course," said Defense Minister Oleksandr Kuzmuk, according to a statement released by ministry spokesman Kostyantyn Khivrenko. 

The Tu-154 aircraft was en route from Tel Aviv, Israel, to the Siberian city of Novosibirsk. It was carrying 76 people, according to Sibir Airlines, from which it was chartered. 

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