WASHINGTON - A U.S. official says investigators are examining the possibility that someone caused the disappearance of a Malaysia Airlines jet with 239 people on board, and that it may have been "an act of piracy."
The official wasn't authorized to speak publicly on the matter and spoke only if not identified. While other theories are still being examined, the official says key evidence for "human intervention" in the plane's disappearance is that contact with its transponder stopped about a dozen minutes before a messaging system quit.
This official says that it's also possible the plane may have landed somewhere.
TIMELINE - Search for the Missing Malaysia Passenger Jet: http://ch7ne.ws/1m43huO
Another communications system on the plane continued to "ping" a satellite for about four hours after contact was lost with the Boeing 777 during a flight from Kuala Lumpur to Beijing -- an indication the plane may have continued to fly on for hours.
Investigator: Missing plane flew over Malaysia
Malaysian investigators are increasingly certain that the missing jetliner turned back across the country after losing communications, and that someone with aviation skills was responsible for the unexplained change in course, according to a government official involved in the probe.
The official, who declined to be identified because he is not authorized to brief the media, said only a skilled person could navigate the Boeing 777 the way it was flown after its last confirmed location over the South China Sea.
Speaking earlier, acting Transport Minister Hishammuddin Hussein said the country had yet to determine what happened to the plane after it dropped off civilian radar and ceased communicating with the ground around 40 minutes into the flight to Beijing.
He said investigators were still trying to establish with certainty that military radar records of a blip moving west across the Malay Peninsula into the Strait of Malacca showed Malaysia Airlines Flight MH370.
"I will be the most happiest person if we can actually confirm that it is the MH370, then we can move all (search) assets from the South China Sea to the Strait of Malacca," he told reporters. Until then, he said, the international search effort would continue expanding east and west from the plane's last confirmed location.
The Malaysian official said it had now been established with a "more than 50 percent" degree of certainty that military radar had picked up the missing plane.
On Thursday, an American official said the plane remained airborne after losing contact with air traffic controllers because it was sending a signal to establish contact with a satellite. The Malaysian official confirmed this, referring to the process by its technical term of a "handshake."
Boeing offers a satellite service that can receive a stream of data on how an aircraft is functioning during flight and relay the information to the plane's home base. Malaysia Airlines didn't subscribe to that service, but the plane still had the capability to connect with the satellite and was automatically sending signals, or pings, said the U.S. official, who spoke on condition of anonymity because he wasn't authorized to discuss the situation by name.
Hishammuddin said the government would only release information about the signals when they were verified.
"I hope within a couple of days to have something conclusive," he told a news conference.
Malaysia has faced accusations it isn't sharing all its information or suspicions about the plane's final movements. It insists it is being open, and says it would be irresponsible to narrow the focus of the search until there is undeniable evidence of the plane's flight path.
No theory has been ruled out in one of modern aviation's most puzzling mysteries.
But it now appears increasingly certain that the plane didn't experience a catastrophic incident over the South China Sea as was initially seen as the most likely scenario. Some experts believe it is possible that one of the pilots, or someone with flying experience, hijacked the plane for some later purpose or committed suicide by plunging the aircraft into the sea.
Mike Glynn, a committee member of the Australian and International Pilots Association, said he considers pilot suicide to be the most likely explanation for the disappearance, as was suspected in a SilkAir crash during a flight from Singapore to Jakarta in 1997 and an EgyptAir flight from Los Angeles to Cairo in 1999.
"A pilot rather than a hijacker is more likely to be able to switch off the communications equipment," Glynn said. "The last thing that I, as a pilot, want is suspicion to fall on the crew, but it's happened twice before."
Glynn said a pilot may have sought to fly the plane into the Indian Ocean to reduce the chances of recovering data recorders, and to conceal the cause of the disaster.
Scores of plane and aircraft from 12 countries are currently involved in the search, which currently reaches into the eastern stretches of the South China Sea and on the western side of the Malay Peninsula, northwest into the Andaman Sea and further into the India Ocean.
India said it was using heat sensors on flights over hundreds of uninhabited Andaman Sea islands Friday and would expand the search for the missing jet farther west into the Bay of Bengal, more than 1,600 kilometers (100 miles) to the west of the plane's last known position. Spokesman Col. Harmit Singh of India's Tri-Services Command said it began land searches after sweeping seas to the north, east and south of the Andaman and Nicobar Islands.
A team of five U.S. officials with air traffic control and radar expertise -- three from the U.S. National Transportation Safety Board and two from the Federal Aviation Administration -- has been in Kuala Lumpur since Monday to assist Malaysia with the investigation.