A Chinese satellite looking for the missing Malaysia Air plane had 'observed a suspected crash area at sea'. Courtesy CNN/Sky News

US investigators are pursuing the possibility that missing Malaysia Airlines Flight MH370 and its 239 passengers and crew are being held against their will at an unknown location.

The Wall Street Journal has this afternoon published sensational claims that counterterrorism officials now believe somebody on board deliberately turned off the plane’s transponders to avoid radar detection.

The report said data automatically downloaded and sent to the ground from the Boeing 777’s engines indicated the plane remained in the air for a total of five hours – a further four hours after contact was lost.

“Officials were told investigators are actively pursuing the notion that the plane was diverted ‘with the intention of using it later for another purpose’,” the paper said, quoting an unnamed source.

A total flight time of five hours after departing Kuala Lumpur means the Boeing 777 could have continued for an additional distance of about 2,200 nautical miles, reaching points as far as the Indian Ocean, the border of Pakistan or even the Arabian Sea, based on the jet’s cruising speed, the paper said.

POLICE RAID HOUSE OF MALAYSIA AIRLINES PILOT

The latest revelation comes as no signs of the missing Malaysian jetliner were found at a spot where Chinese satellite images showed what might be plane debris, Malaysia’s civil aviation chief said in the five-day hunt for the plane.

“There is nothing. We went there, there is nothing,’’ Azharuddin Abdul Rahman told reporters in Kuala Lumpur.

News_Image_File: This image, first released by CCTV America, shows an object in the ocean spotted by Chinese satellites on Sunday. Picture: Supplied

Vietnamese officials previously said the area had been “searched thoroughly’’ in recent days.

The officials said the site in the South China Sea where Chinese satellite pictures allegedly showed the missing Malaysia Airlines Flight MH370 had been “searched thoroughly’’ in recent days.

The reported sighting of wreckage was considered to be the first major lead in the search for the missing plane. China’s State Administration for Science, Technology and Industry for National Defence (SASTIND) last night published three satellite images.

The images appeared to show three floating objects in the sea were captured just one day after the plane carrying 239 disappeared.

Chinese authorities and some aviation experts cautioned about the debris and said it could provide false hope.

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China’s civil aviation chief, Li Jiaxiang, said there was no proof that the objects in the South China Sea were connected to the missing commercial aircraft.

One US official close to the plane investigation also said the Chinese satellite report was a “red herring.”

The Chinese satellite spotted three blips of varying sizes, the largest of which is 24m by 22m. The missing Boeing 777-200ER jet had a wingspan of 60.9 metres and a length of 63.7 metres.

Chinese agency SASTIND gave coordinates of 105.63 east longitude, 6.7 north latitude, which would put it in waters northeast of where MH370 took off in Kuala Lumpur, Malaysia, south of Vietnam and close to where the plane lost contact with air traffic control.

Pham Quy Tieu, deputy Vietnamese transport minister, told The Associated Press that the area had been “searched thoroughly” by forces from other countries over the past few days.

Tom Haueter, former aviation director of the US National Transportation Safety Board, was also sceptical that the images were connected with the missing jet.

“Any aircraft structure that size would sink. It wouldn’t float like this,” he said. “I don’t believe it’s the plane. We don’t have enough data to say what happened.”

News_Image_File: Another satellite image, first released to CCTV America. Experts said the Chinese images are not high resolution. Picture: Supplied

However, another former US aviation safety official said the images represent the first solid lead consistent with the Malaysia Airlines plane’s flight path.

Peter Goelz, former managing director of the US federal National Transportation Safety Board, told CNN: “These (images) are the first solid piece of evidence we have that are on the correct flight path.”

Governments involved in the search have not confirmed whether the blips are the wreckage of the missing flight.

US Navy spokesman Commander William Marks, of the Seventh Fleet, said the SASTIND satellite data had not yet been corroborated by US satellites.

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News_Image_File: A third satellite image released by China’s State Administration for Science, Technology and Industry. Picture: Supplied

News_Module: Malaysia Search Area

China’s civil aviation chief was also quoted by Reuters saying he could not confirm that the objects were the wreckage of the missing aircraft.

“Chinese satellites have found smoke and floating objects ... At present we cannot confirm this is related to the missing aircraft,” Li Xiaxiang said.

Commander Marks said if the floating objects are as big as Chinese satellite data suggests, “it’s something that (American military) radars would pretty easily pick up”.

China has provided no explanation as to why the images were only released today. There were 153 Chinese nationals on board the flight.

Malaysia’s civil aviation chief, Datuk Azharuddin Abdul Rahman, said Malaysia had not been officially informed by China about the images.

He said if Beijing informs them of the co-ordinates, Malaysia will dispatch vessels and planes immediately.

“If we get confirmation, we will send something,” he told the Associated Press early Thursday.

News_Image_File: Let’s go: Indonesian air force prepare to launch a search aircraft. Picture: AFP

Final words from the cockpit

The mystery of the plane’s missing hour

Search teams will be hoping to locate the aircraft’s emergency locator transmitter, which acts as a beacon. However, aviation experts have warned they do not always work when involved in a major crash into water, the BBC reports.

The black box can also act as an alert system, however the signal is not able to be detected over long distances.

Why the black box won’t help: A pilot tells news.com.au

News_Image_File: A Vietnamese air force helicopter scans the sea for signs of wreckage. Picture: AFP

News_Image_File: Desperate search: An Indonesian rescuer scans the seas in the Malacca Strait. Picture: AFP

The missing Boeing 777-200ER took off from Kuala Lumpur bound for Beijing at 12.41am local time (3:41am AEDT) on Saturday.

The plane vanished off the radar around 50 minutes later at 1.30am. No distress signal was sent.

An international air and sea search involving 12 countries has entered its sixth straight day, with authorities combing a search zone of 27,000 square nautical miles (93,000 square km).

The search effort has focused on two areas, the Malacca Strait and the South China Sea.

In a statement Thursday afternoon, Malaysia Airlines announced it has retired the flight call signs MH370 and MH371 “out of a mark of respect.”

“As a mark of respect to the passengers and crew of MH370 on 8 March 2014, the MH370 and MH371 flight codes will be retired from the Malaysia Airlines’ Kuala Lumpur — Beijing/ Beijing — Kuala Lumpur,” the airliner said.

News_Module: Malaysian airspace activity

Some of the possible causes for the plane’s sudden disappearance include a catastrophic structural failure of the jet’s airframe or its Rolls-Royce Trent 800 engines.

Last September, authorities issued a global warning regarding the structural integrity of 777 aircraft following reports of cracks and corrosion appearing in the fuselage skin, resulting in a “weak spot”.

Another possibility is that it continued to fly despite a failure of its electrical systems, which could have knocked out communications, including transponders that enable the plane to be identified by commercial radar.

Pilot disorientation and suicide have also been suggested, along with terrorism.

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With wire services AFP and AP