BEIJING — Malaysias prime minister Saturday provided the strongest official confirmation yet that Malaysia Airlines flight 370 vanished because of a criminal act, as authorities in Kuala Lumpur launched a search of the home of the pilot.At a press conference in Kuala Lumpur, Prime Minister Najib Razak said that investigators have determined that the Beijing-bound flight was deliberately diverted from its planned route, with its communications turned off. He said authorities had ended their search in the South China Sea and suggested that the plane flew into one of two vast areas hundreds of miles west of its intended route.In view of this latest development, the Malaysian authorities have refocused their investigation into the crew and passengers on board, said Najib, adding that investigators are still investigating all possibilities as to what caused MH 370 to deviate from its original flight path.Najib timed his news conference to deal with mounting frustrations from within China and other countries over Malaysias handling of an airliner missing for more than seven days. The flight carried 239 people, two-thirds of whom were Chinese, and Huang Huikang, Chinas ambassador to Malaysia, could been seen sitting in the front row of the news conference, held at a hotel outside of Kuala Lumpur, Malaysias capital. After the news conference, in which Najib took no questions from reporters, a Chinese Foreign Ministry spokesman issued a stern statement urging Malaysia to continue providing it with thorough and exact information about MH 370.An editorial by Chinas state-run Xinhua news service later was blistering. "It is undeniable that the disclosure of such vital information is painfully belated -- more than seven excruciating days after the 227 passengers and 12 crew members lost contact with their beloved relatives and friends, it said.And due to the absence -- or at least lack -- of timely authoritative information, massive efforts have been squandered, and numerous rumors have been spawned, repeatedly racking the nerves of the awaiting families.Najibs comments further suggest that someone with significant flying experience must have commandeered the flight, or that a hijacker managed to coerce the crew to take two actions that diverted the flight from reaching Beijing. One involved disabling the flights Aircraft Communications Addressing and Reporting System over the northeast coast of Malaysia. Then, at 1:21 a.m, someone turned off a transponder that was reporting the aircrafts location, altitude, speed and other information.Forensics work and a review of Malaysian radar, Najib said, has now revealed that MH 370 turned back and started traveling in a westerly direction. But the flight was still tracked by satellites overhead. A review of that data, Najib said, revealed that the last confirmed communication between the plane and the satellite was at 8:11 a.m. Malaysian time last Saturday, nearly seven hours after air traffic controllers lost track of it. Based on this new data, the prime minister said, investigators think the plane could have traveled in two possible directions a northern corridor stretching approximately from the border of Kazakhstan and Turkmenistan to northern Thailand, or a southern corridor stretching approximately from Indonesia to the southern Indian ocean. An international search effort has already shifted its attention to those areas, he said. That first scenario raises the possibility that a hijacker or hijackers could have attempted to land the plane and its passengers in a remote part of Central Asia known to harbor militant groups. But in an age of satellites, doing so undetected would be extremely difficult, and so far theres been no reported claim of responsibility for the planes disappearance. Citing an unnamed police official, Reuters reported that authorities began searching the home of the flights pilot, Zaharie Ahmad Shah, after the prime ministers news conference. That triggered questions about why Malaysian investigators had waited so long to seriously investigate the 53-year-old pilot.According to Malaysia Airlines, Zaharie joined the airline in 1981 and was certified by Malaysias Department of Civil Aviation as a simulator test examiner. He had 18,365 flying hours. His co-pilot, Fariq Abdul Hamid, 27, had 2,763 hours of flying and has been the focus of recent publicity over a possible breach of post-9/11 security rules. Last week, an Australian TV station reported that Fariq and a pilot invited two women to join them in the cockpit on a flight from Thailand to Malaysia in 2011, where they posed for photos.Prior to Najibs statement, leaks from unnamed U.S. officials to news agencies suggested that the flight may have vanished because of a criminal act. The New York Times reported the aircraft dramatically changed its altitude after losing contact last Saturday with ground control, and altered its course more than once as if still under the command of a pilot.Radar signals recorded by the Malaysian military appeared to show that the missing airliner climbed to 45,000 feet, above the approved altitude limit for a Boeing 777-200, soon after it disappeared from civilian radar and turned sharply to the west, the newspaper reported late Friday.On Saturday, the Associated Press quoted an unnamed Malaysian official as saying it was conclusive the flight was hijacked.But Najib seemed to hedge on that point with his statement. Despite media reports that the plane was hijacked, I wish to be very clear: We are still investigating all possibilities as to what caused MH 370 to deviate from its original flight path.In the initial days after the flights disappearance, Chinese friends and relatives of MH 370 passengers were holed up in a ballroom of a Beijing hotel, angered by the lack of news from Malaysia Airline officials. Some flying to Kuala Lumpur in hopes of being better informed. Malaysian authorities initially said they would follow up Najibs appearance with a news conference Saturday afternoon where reporters could ask questions. Soon after Najib finished his statement, they canceled that later news conference.