KUALA LUMPUR, March 15 — Speculation that missing Malaysia Airlines flight MH370 completely evaded all radar to land undetected was implausible, US Federal Bureau of Investigation (FBI) officials have concluded.

With the probe into the disappearance of the Beijing-bound flight with 239 onboard now starting to focus on possible foul play, this leaves only the possibility that the Boeing 777 ―  now missing for over a week ― was somewhere at the bottom of an ocean or sea.

According to a report by the New York Times, investigators examining the suspicion that the airliner was hijacked and subsequently landed at a hidden location to be repurposed for a possible terrorist use later, have dismissed the idea.

Given the closely-guarded borders in Southeast Asia and the tensions between India and Pakistan, investigators concluded that it was not likely that the numerous military radar stations within the theoretical 4,400-mile radius of MH370’s range would have missed it attempting to enter a country’s airspace.

“... the idea it could cross into Indian airspace and not get picked up made no sense,” an unnamed investigator told the NYT.

The FBI investigators also pointed out that at nearly 70m long and weighing over 140 tonnes unladen, the jumbo jet would have required a long runway to land -- not the size of the typical hidden airfield.

Earlier today, other anonymous US investigators and a “highly-placed Malaysian source” arrived at the conclusion that the plane caught by military radar turning back from the east coast of peninsular Malaysia and flying west of Penang was MH370.

Yesterday, satellite communications firm Inmarsat revealed it continued to receive “pings” from MH370 after it lost signal, reinforcing the belief it flew on after Malaysian radar lost sight of the plane.

The combination of available information is now leading investigators “to believe that it either ran out of fuel or crashed right before it ran out of fuel,” the NYT added.

Search efforts now include the millions of square kilometres in the Indian Ocean.

The disappearance of MH370 40 minutes after it departed Kuala Lumpur International Airport for Beijing on March 8 was described by the Department of Civil Aviation (DCA) as an “unprecedented mystery”.

The Boeing 777 — considered one of the most reliable in aviation history — went dark without ever issuing any distress signals, leading investigators to believe that these were disabled manually.

The probe is now beginning to narrow down on foul play, with a hijacking the most plausible scenario.

An ongoing search using the aerial and naval assets of 12 countries over the past week has not yielded a single shred of evidence on the whereabouts of the missing plane.