Xinhua said the Chinese ambassador to Malaysia made the statement Tuesday to media in Kuala Lumpur.
There has been some speculation that Uighur separatists in far western Xinjiang province might have been involved with the flight's disappearance.
The statement will lessen that speculation.
Xinhua also reported that Chinese authorities have begun searching for the plane on Chinese territory.
There were 154 Chinese among the 227 passengers aboard on Flight 370, which went missing March 8 on its way to Beijing.
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