The last words from a Malaysian passenger jet missing for 10 days were apparently spoken by the co-pilot, the airline said Monday, providing a glimpse into the crucial period when the plane was deliberately diverted.

Clarification that the voice was most likely that of First Officer Fariq Abdul Hamid came during a press conference at which Malaysian officials hit back at "irresponsible" suggestions that they had misled the public -- and passengers' relatives -- over what happened to Malaysia Airlines Flight 370.

The last words from a Malaysian passenger jet missing for 10 days were apparently spoken by the co-pilot, the airline said Monday, providing a glimpse into the crucial period when the plane was deliberately diverted.

Clarification that the voice was most likely that of First Officer Fariq Abdul Hamid came during a press conference at which Malaysian officials hit back at "irresponsible" suggestions that they had misled the public -- and passenger's relatives -- over what happened to Malaysia Airlines Flight 370.

Malaysia said Sunday the number of countries searching for a missing airliner had nearly doubled to 25 as a full-scale criminal probe into its disappearance got under way, with particular scrutiny of the pilots.

Transport Minister Hishammuddin Hussein said the number of participating countries had jumped from 14 to 25 as the search for the aircraft focused on two vast, and vastly contrasting, land and ocean transport corridors. The dramatic "re-calibration" will inevitably bring "new challenges of coordination and diplomacy", the minister said.

Malaysia said Sunday that police had searched the homes of the pilots of a missing jet and examined a home flight simulator after revelations that the flight was deliberately diverted triggered a full-scale criminal probe.

As a multi-nation operation began a new push to locate the vanished Boeing-777 somewhere within a vast arc of land and ocean, criminal investigators sought other clues to the fate of the Malaysia Airlines plane.

A missing Malaysian airliner was apparently deliberately diverted and flown for hours after vanishing from radar, Prime Minister Najib Razak said Saturday, in an announcement that stopped short of confirming a hijack but took the "excruciating" jet drama into uncharted new territory.

Najib said investigators believed "with a high degree of certainty" that Malaysia Airlines flight 370's communications systems were manually switched off, and that the plane veered westward in a fashion "consistent with deliberate action" after dropping off primary radar.

Malaysia said Friday it was dramatically expanding the already vast scope of its search for a missing passenger plane, admitting it was no closer to solving the agonizing aviation mystery a week after the jet vanished.

"The aircraft is still missing, and the search area is expanding," said Transport Minister Hishammuddin Hussein.

A U.S. naval ship is headed from the Gulf of Thailand to the Strait of Malacca as efforts to find a missing Malaysian airliner shift focus, officials said Wednesday.

The USS Kidd, a guided missile destroyer, has been taking part in the near week-long hunt for Malaysia Airlines flight 370 along with another American destroyer and a P-3 Orion surveillance aircraft.

Malaysia said Thursday that satellite images of suspected debris from a missing jet were yet another false lead, and debunked a report the plane had flown on for hours after losing contact -- leaving the nearly week-old mystery no closer to being solved.

China had sparked talk of a breakthrough in the riddle of the Malaysia Airlines (MAS) jet with satellite images of three large floating objects near where flight 370 with 239 people on board lost contact on Saturday, en route from Kuala Lumpur to Beijing.

The captain of a missing Malaysian jet is said to be an engineering buff who assembled his own flight simulator, while friends of the co-pilot are defending his reputation after one report portrayed him as a cockpit Casanova.

Malaysian Airlines flight 370 disappeared six days ago and an international search and rescue effort in waters around Southeast Asia has failed to find a shred of evidence in one of the biggest aviation mysteries in history.

U.S. investigators suspect a missing Malaysian airliner was in the air for four hours after its last confirmed contact, the Wall Street Journal reported Thursday, deepening the mystery surrounding the disappearance.

It said U.S. aviation investigators and national security officials are basing their theory on data automatically downloaded and sent to the ground from the Rolls Royce engines, which suggested the Boeing 777 flew for a total of five hours.