A senior Malaysian official says a signaling system was partially disabled on the missing Malaysia Airlines jet before a pilot spoke to air traffic control without hinting at any trouble.
Malaysia's defense minister said Sunday the final words from the cockpit were spoken to Malaysian air traffic controllers after the plane's data communication system had been partially disabled.
The pilots did not mention any trouble on board, suggesting they may have been misleading ground control or acting under coercion by someone familiar with aviation technology.
The development could help investigators determine why the plane turned far off its planned route and vanished from radar screens more than a week ago with 239 people onboard.
Police have searched the homes of the two pilots and are examining an elaborate flight simulator taken from one of them. Authorities are also questioning engineers who may have had contact with the plane before it left Kuala Lumpur.
Meanwhile, Malaysia appealed for international coordination in the search for the missing passenger jet that stretches across two corridors from the Caspian Sea to the southern Indian Ocean.
Malaysian officials say the number of countries involved in the search has grown to 25 after it was determined the plane may have flown as far north as Central Asia.
Authorities briefed envoys on the progress of the investigation after calling off a search in the South China Sea, marking a new diplomatic phase in a search operation thought increasingly likely to rely on the sharing of sensitive material such as military radar data.
A full-scale criminal investigation was triggered when Malaysian Prime Minister Najib Razak said Saturday there is a "high degree of certainty" that someone who knew what he was doing deliberately turned off the jet's communications systems.
The prime minister said the last of the systems were switched off just before the jet turned westward, away from its flight path. Mr. Najib stopped short of saying the plane was hijacked and said investigators are looking at all scenarios.
The search for Malaysia Airlines Flight 370 now ranges from Kazakhstan to the southern Indian Ocean. Investigators say the plane had enough fuel to fly for several hours after disappearing from radar Saturday, March 8.
Authorities have also not ruled out the possibility the plane was on the ground at an unknown location when some satellite signals were sent.
The missing Boeing 777 was flying from Kuala Lumpur to Beijing when it disappeared. About two-thirds of the people on board were Chinese. Other passengers included Europeans and Americans.