Intelligence checks on the 153 Chinese passengers aboard a missing Malaysian airliner produced no red flags, China said Tuesday, as investigators struggled to clarify events that led to the plane's dramatic disappearance.
Lending fresh weight to the belief that the plane was deliberately diverted, the New York Times reported that the first turn it made off its flight path was programmed into the aircraft's computer navigation system, probably by someone in the cockpit.
Rather than manually operating the plane's controls, whoever altered Flight 370's path typed seven or eight keystrokes into a computer situated between the captain and the co-pilot, the report said, quoting US officials.
Eleven days after contact was lost with the aircraft and its 239 passengers and crew, there has been minimal progress in determining precisely what happened or where the plane ended up.
Two thirds of those on board were Chinese, and Malaysia had asked the authorities in Beijing to run an exhaustive background check on all their nationals as part of a probe into everyone aboard.
Particular attention was paid to a passenger from China's Muslim ethnic Uighur minority, separatist elements of which have become increasingly militant in their struggle against Chinese rule.
On Tuesday, China's ambassador to Malaysia Huang Huikang said no evidence had been found that would link anyone to a possible hijacking or terrorist attack on the jet, the official Xinhua news agency reported.
Huang also said China had begun searching for the aircraft in its own territory.
The potential search area, which was only properly identified after a week of fruitlessly scouring the South China Sea, is enormous -- stretching from the depths of the Indian Ocean, up and over the Himalaya and into central Asia.
China's state media has been vocally critical of Malaysia's handling of the missing plane investigation, saying valuable time and resources were wasted in the hours and days immediately after the aircraft disappeared on March 8.
Desperate relatives of the Chinese passengers threatened to go on hunger strike Tuesday, demanding that Malaysia's ambassador brief them in person.
"Relatives are very unsatisfied. So you hear them saying 'hunger strike'," Wen Wancheng, whose son was aboard the missing flight, told reporters at the Beijing hotel where families are gathered.
Malaysian officials insist they are investigating all the passengers and crew, but for the moment the focus is clearly on the two pilots -- Captain Zaharie Ahmad Shah and First Officer Fariq Abdul Hamid.
US lawmaker Michael McCaul, chairman of the House Homeland Security Committee, has said that so far the probe "all leads towards the cockpit, with the pilot himself, and the co-pilot."
On Monday the head of Malaysia Airlines, Ahmad Jauhari Yahya, revealed that the last recorded words from the cockpit -- "All right, good night" -- were almost certainly spoken by the co-pilot, Fariq.
The airline boss said the Boeing's Aircraft Communications Addressing and Reporting System (ACARS) could have been switched off before or after Fariq spoke, correcting an earlier chronology in the investigation's latest stumble.
Police have searched both pilots' homes and are examining a flight simulator that Captain Zaharie, 53, had assembled at his home.
Malaysian media reported that the captain is distantly related to the daughter-in-law of opposition leader Anwar Ibrahim, adding to speculation after it emerged he was also a member of his political party.
Anwar said Tuesday he was "disgusted" by the suggestion the plane may have been sabotaged as an act of revenge after he was convicted on a sodomy charge widely seen as politically motivated.
Twenty-six countries are now involved in searching for the jet in a northern corridor over south and central Asia, and a southern corridor stretching deep into the southern Indian Ocean towards Australia.
A French expert who took part in the search for Air France Flight 447, which crashed in the Atlantic Ocean in 2009, said finding the Malaysian plane was a much tougher proposition.
"Here we simply have no idea of the location of the aircraft, because there were no ACARS signals," said Jean-Paul Troadec, a special adviser with France's civil aviation accident investigation agency.
Although automated systems transmissions from AF447 helped identify the crash site, it still took two years to locate and recover the "black boxes" from the ocean floor.
Troadec is one of three French investigators in Kuala Lumpur advising the Malaysian authorities.
Malaysia has deployed its navy and air force to the southern corridor, where Australia is taking the lead in scouring a huge section of ocean off its west coast.
"It will take at least a few weeks to search the area thoroughly," said John Young of the Australian Maritime Safety Authority.
The US Pacific Fleet said it was withdrawing a guided missile destroyer because the area was simply too big for such a vessel to make an effective contribution, and that two long-range patrol aircraft would now take the lead.
"The Indian Ocean goes so far, there probably aren't enough ships and aircraft in the world to search every inch of it," Fleet spokesman Commander William Marks told CNN.
"It's kind of like saying, all right, I want to find a person somewhere between New York and California. I just don't know where they are."