As a search for debris sighted by Chinese satellites proved fruitless on Thursday according to Malaysian officials, United States investigators said they suspected the missing Malaysia Airlines aircraft flew for about four hours past the time of its last contact.

Quoting two people briefed on details sourced from engine data transmitted from the Boeing 777, the Wall Street Journal reported the plane "stayed in the air for about four hours past the time it reached its last confirmed location, ... raising the possibility that the plane could have flown on for hundreds of additional miles under conditions that remain murky."

Malaysian officials said the plane lost contact with air traffic control around one hour after taking off from Kuala Lumpur early on Saturday, over the Gulf of Thailand, where search efforts have been, so far, been concentrated.

But the Wall Street Journal said US counterterrorism officials were now "pursuing the possibility that a pilot or someone else on board the plane may have diverted it toward an undisclosed location after intentionally turning off the jetliner's transponders to avoid radar detection".

The report came as China said its satellites had found "three floating objects" near a suspected crash site of the missing Malaysia Airlines Boeing 777, as search operations continued for a sixth day. Malaysia's civil aviation chief said later no signs of the aircraft were found at the location, the Associated Press reported from Kuala Lumpur.

The release of the satellite images came as China's Premier said his government would pursue any leads in the search for the aircraft, which carried on board 5 Indians, 154 Chinese, 38 Malaysians and nationals of Indonesia, the U.S., France and half a dozen other countries.

"We will not give up on any suspected clue," Premier Li Keqiang told reporters at his annual press conference with domestic and foreign journalists, following the conclusion of the week-long Chinese Parliament session. "We are also looking very closely at all suspected clues shown on satellite images," he said.

China's State Administration of Science, Technology and Industry for National Defence said on its website late on Wednesday three suspected objects were found spread across an area with a radius of 20 km. The largest of the three pieces was around 70 feet in length and width.

The agency said the objects were found at the coordinates 6.7 degrees north latitude and 105.63 degrees east longitude, the State-run Xinhua news service reported, although aviation officials said a review could not confirm a link to the aircraft.

Amid frustration and rising despair for the relatives of passengers, the Chinese Premier said the government was "deeply concerned" over the safety of the missing.

"Those people's families and friends are burning with anxiety," he told reporters. "Currently, 8 Chinese vessels are in the related waters and one is on the way. Ten satellites are being used to provide information and technical support. As long as there is a glimmer of hope, we will not stop searching for the plane."

The possible lead from satellite images in the search for the missing aircraft came amid confusion over its last point of contact.

Malaysia's air force chief Rodzali Daud on Wednesday denied saying military radar had tracked the flight more than one hour after its last contact with civilian air traffic control over the Gulf of Thailand, northeast of Malaysia. Military officials had said a day earlier the aircraft had been tracked far west of its last point of contact, over the Straits of Malacca west of the country.

Search operations were markedly widened on Wednesday, extending beyond the initial focus over the Gulf of Thailand to the Malacca Straits and west to the Andaman Sea. More than 10 countries have now dispatched ships or planes to assist in rescue efforts, with India and Japan on Wednesday becoming the latest countries to pledge their support.

With U.S. investigators now suggesting the aircraft may have flown for four more hours, that search area could now possibly be further widened.

The Wall Street Journal report said "the huge uncertainty about where the plane was headed, and why it apparently continued flying so long without working transponders" had "raised theories among investigators that the aircraft may have been commandeered for a reason that appears unclear to U.S. authorities".

Officials were told investigators were "actively pursuing the notion that the plane was diverted with the intention of using it later for another purpose."

(This report was first published in >The Hindu online edition .)

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