SEPANG – Malaysia turned the search for Flight 370 into a criminal investigation on Saturday, after the prime minister declared in a news conference that the plane had been deliberately diverted from its planned route a week ago from Kuala Lumpur to Beijing. The plane then flew as much as seven hours to an unknown destination.
The prime minister, Najib Razak, said in a news conference on Saturday afternoon that Malaysia would seek the help of other governments across a large region of Asia in trying to find the plane.
Malaysian authorities later released a map showing that the last satellite signal received from the plane had been sent from a point somewhere along on one of two arcs spanning large distances across Asia.
In other developments Saturday, police officers were seen arriving at the gated residential compound where the flight’s pilot, Zaharie Ahmad Shah, had his home, and Malaysian news media reported that a raid was underway. A police spokeswoman declined to comment, saying that no details would be available until a news conference early Sunday evening.
According to Mr. Najib, satellite orbiting 22,250 miles (35,800 kilometers) over the middle of the Indian Ocean had received a transmission that, based on the angle of transmission from the plane, came from a location somewhere along one of two arcs. One arc ran from the southern border of Kazakhstan in Central Asia to northern Thailand. The other arc ran from near Jakarta, Indonesia, to the Indian Ocean, roughly 1,000 miles off the west coast of Australia.
“These movements are consistent with deliberate action by someone on the plane,” Mr. Najib said. He noted that one communications system had been disabled as the plane flew over the northeast coast of Malaysia. A second system, a transponder aboard the aircraft, abruptly stopped broadcasting its location, altitude, speed and other information a few minutes later, at 1:21 a.m., while the plane was one-third of the way across the Gulf of Thailand from Malaysia to Vietnam.
Mr. Najib’s news conference, at an airport hotel here on the outskirts of Kuala Lumpur, came a day after American officials and others familiar with the investigation told The New York Times that Flight 370 had experienced significant changes in altitude after it lost contact with ground control, and altered its course more than once as if still under the command of a pilot.
Military radar data subsequently showed that the aircraft turned and flew west across northern Malaysia before arcing out over the wide northern end of the Strait of Malacca, headed at cruising altitude for the Indian Ocean.
The disappearance of the jet has mesmerized many in China, partly because nearly two-thirds of the 239 people aboard were Chinese citizens. After Mr. Najib’s statement Saturday, the Chinese Ministry of Foreign Affairs demanded to know more, and said that China was sending technical experts to Malaysia.
“We ask that the Malaysian side provide even more comprehensive and accurate information,” the spokesman Qin Gang said in a statement on the ministry’s website. “We urge that based on the new circumstances, Malaysia further expand and clarify the scope of the search and intensify search efforts, and we ask that Malaysia call on even more countries to become involved in the search.”
Huang Huikang, China’s ambassador to Malaysia, sat impassively in a light gray suit in the front row of Mr. Najib’s news conference.
The flight had been scheduled to land at 6:30 a.m. in Beijing, so the latest time given by Mr. Najib — 8:11 a.m. — could have been toward the end of the time the plane’s fuel was scheduled to run out.
“The investigation team is making further calculations, which will indicate how far the aircraft may have flown after the last point of contact,” Mr. Najib said, reading a statement in English. “Due to the type of satellite data, we are unable to confirm the precise location of the plane when it last made contact with a satellite.”
The northern arc described by Mr. Najib passes through or close to some of the world’s most volatile countries that are home to insurgent groups, but also over highly militarized areas with robust air-defense networks, some run by the American military. The arc passes close to northern Iran, through Afghanistan and northern Pakistan, and through northern India and the Himalayan mountains and Myanmar.
An aircraft flying on that arc would have to pass through air-defense networks in India and Pakistan, whose mutual border is heavily militarized, as well as through Afghanistan, where the United States and other NATO countries have operated air bases for more than a decade.
Air bases near that arc include Bagram Airfield in Afghanistan, where the United States Air Force’s 455th Air Expeditionary Wing is based, and a large Indian air base, Hindon Air Force Station.
The Indian Ocean, the third-largest in the world, has an average depth of more than 12,000 feet, or more than two miles.
Mikael Robertsson, a founder of Flightradar24, a global aviation tracking service, said the way the plane’s communications were shut down pointed to the involvement of someone with considerable aviation expertise and knowledge of the air route, possibly a crew member, willing or unwilling.
The Boeing’s transponder was switched off just as the plane passed from Malaysian to Vietnamese air traffic control space, thus making it more likely that the plane’s absence from communications would not arouse attention, Mr. Robertsson said by telephone from Sweden.
“Always when you fly, you are in contact with air traffic control in some country,” he said. “Instead of contacting the Vietnam air traffic control, the transponder signal was turned off, so I think the timing of turning off the signal just after you have left Malaysian air traffic control
indicates someone did this on purpose, and he found the perfect moment when he wasn’t in control by Malaysia or Vietnam. He was, like, in no-man’s country.”
According to a person who has been briefed on the progress of the investigation, the two “corridors” described by Mr. Najib were derived from calculations made by engineers from the satellite communications company Inmarsat, which were provided to investigators. The person spoke on condition of anonymity because details of the search operation remain confidential.
The satellite communications box fitted on the plane is of an older generation and is not equipped with a global positioning system, the person said. But investigators have managed to calculate the distance between the “ping” from the plane and a stationary Inmarsat-3 satellite orbiting above the Equator and over the Indian Ocean.
The satellite can “see” in an arc that stretches to the north and south of its fixed position, but without GPS it can only say how far away the ping is, not where it is coming from, the person said.
“Imagine a torch beam coming from a satellite going left and right,” the person said, referring to a flashlight beam. “It is the maximum arc in the two directions that is being calculated.”
But based on what is already known about the flight’s trajectory, investigators are strongly favoring the southern corridor as the likely flight path, the person said. “The U.S. Navy would not be heading toward Kazakhstan,” the person said.