Hong Kong (CNN) Search efforts may be closing in on the wreckage of a Japanese F-35 stealth fighter that crashed into the Pacific Ocean two weeks ago, perplexing investigators and raising questions about the reliability of world's most-advanced warplane.

"We have a pretty good idea where it is," a senior US Navy official told CNN this week, adding that the search area was looking at depths around 1,500 feet (450 meters), far shallower than the 5,000 feet (1,500 meters) that had been speculated, and a depth that would make recovery operations much easier.

The US-designed F-35 is considered to be the best stealth jet technology in operation. It's sudden and unexplained disappearance from radar just minutes into a training flight over the Pacific has raised concerns that China or Russia could try to get to access to the wreckage, though both US and Japanese officials have dismissed the idea.

In response to a question regarding the security of the wreckage during a visit to Washington last week, Japanese Defense Minister Takeshi Iwaya said the country's naval forces were keeping close watch on the search area.

On Tuesday, Iwaya announced plans to dispatch a civilian deep-sea research vessel to the search area east of the northern tip of the Japanese main island of Honshu .

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