The remarks will dampen speculation that Uighur Muslim separatists in the far-western Xinjiang province might have been involved in the disappearance of the Boeing 777 and its 239 passengers and crew early on March 8.
The plane was carrying 154 Chinese passengers when someone on board deliberately diverted it from its route to Beijing less than one hour into the flight, according to Malaysian officials. A massive search operation in the Indian Ocean and beyond has yet to find any trace of the plane.
Chinese Ambassador to Malaysia Huang Huikang said background checks on the Chinese nationals on the plane didn’t uncover any evidence suggesting they might have been involved in a hijack or terror attack, according to the state news agency Xinhua.
Uighur groups have been involved in attacks inside China and some have a presence in the Afghan-Pakistan border area, where Al-Qaeda and other transnational jihadi groups are based.
Malaysian police are investigating the plane’s pilots and ground engineers and have asked intelligence agencies from countries with passengers on board to carry out background checks on them.
Malaysian authorities say that someone on board the flight switched off two vital pieces of communication equipment, allowing the plane to fly almost undetected. Satellite data shows it might have ended up somewhere within a giant arc stretching from Central Asia to the southern reaches of the Indian Ocean.
Huang said China had begun searching for the plane on its territory, but gave no details. When asked at a Foreign Ministry briefing in Beijing on Tuesday what the search involved, Ministry spokesman Hong Lei said only that satellites and radar were being used.
A Chinese civilian aviation official has previously said there was no sign of the plane entering the country’s airspace on commercial radar. The government has not said whether this has been confirmed by military radar data.
Malaysian police say they are investigating the possibility of hijacking, sabotage, terrorism and issues related to the mental health of the pilots or anyone else on board, but have yet to give an update on what they have uncovered.
Malaysian military radar last spotted the plane in the northern reaches of the Strait of Malacca at 2:14 am on March 8, just over one-and-a-half hours after it took off from Kuala Lumpur. A signal to a satellite from the plane at 8:11 am, suggested that, by then, the plane was somewhere in a broad arc spanning from Kazakhstan to the Indian Ocean, west of Australia.
Investigators are scouring what little data they have to try and determine who was in control of the plane when it stopped communicating. They have indicated that whoever it was must have had aviation experience and knowledge of commercial flight paths.
On Monday, Malaysian Airlines chief executive Ahmad Jauhari Yahya said an initial investigation indicated that the last words ground controllers heard from the plane—“All right, good night”—were spoken by the co-pilot, Fariq Abdul Hamid.
On Sunday, the Defense Minister Hishammuddin Hussein had said these words were spoken before the jetliner’s data communications systems—the Aircraft Communications Addressing and Reporting System (ACARS)—had been switched off, suggesting the voice from the cockpit was knowingly deceiving ground controllers.
But Ahmad made a potentially significant change to that timeline. Speaking alongside Hishammuddin, he said that although the final data transmission from ACARS, which gives plane performance and maintenance information, came before the co-pilot’s words, it was still unclear at what point the system was switched off.
The search for the plane is one of the largest in aviation history, and now involves 26 countries. It was initially focused on seas on either side of Peninsular Malaysia—in the South China Sea and the Strait of Malacca. It has since expanded to include the Indian Ocean and the Bay of Bengal as well as 11 countries to the northwest that the plane could have, in theory, crossed, including China and India.
US, Australian and Indonesian planes and ships are searching waters to the south of Indonesia’s Sumatra Island all the way down to the southern reaches of the Indian Ocean.
China was also sending ships to the Indian Ocean, where they will search two blocks of sea covering a total of 186,000 square miles (300,000 square kilometers)—three times the area already searched in the South China Sea.
The area being covered by the Australians is even bigger—232,000 square miles (600,000 square kilometers)—and will take weeks to search thoroughly, the manager of Australian Maritime Safety Authority’s emergency response division John Young, said.
He added: “This search will be difficult. The sheer size of the search area poses a huge challenge—a needle in a haystack remains a good analogy.”