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

Confirmation that the voice was First Officer Fariq Abdul Hamid’s 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.

China has led some harsh criticism of the Malaysian authorities, suggesting they withheld important information and were slow to act, hampering the search for the Boeing 777 in its crucial early days.

Captain Zaharie Ahmad Shah and his co-pilot Fariq Abdul Hamid have become a primary focus of the investigation, with one of the key questions being who was in control of the aircraft when it was deliberately taken off course about an hour into its flight to Beijing.

The last message from the cockpit -- “All right, good night” -- came around the time that two of the plane’s crucial signalling systems were manually disabled.

“Initial investigations indicate it was the co-pilot who basically spoke,”

Malaysia Airlines CEO Ahmad Jauhari Yahya told reporters.

The last signal from the Aircraft Communications Addressing and Reporting System (ACARS) was received 12 minutes before the co-pilot’s seemingly nonchalant final words.

ACARS transmits key information on a plane’s condition.

The plane’s transponder -- which relays the plane’s location -- was switched off just two minutes after the voice message.

US intelligence efforts have also focused on the cockpit crew, according to a senior US lawmaker.

“I think this all leads towards the cockpit, with the pilot himself, and co-pilot,” said Michael McCaul, chair of the House Homeland Security Committee, citing information he had received in intelligence briefings.

The plane went missing early on March 8 with 239 passengers and crew aboard, spawning a massive international search across Southeast Asia and the Indian Ocean that has turned up no trace of wreckage.

Two-thirds of the passengers were Chinese, and state-controlled media in China attacked Malaysia anew on Monday.

“The contradictory and piecemeal information Malaysia Airlines and its government have provided has made search efforts difficult and the entire incident even more mysterious,” the state-controlled China Daily newspaper wrote in an editorial.

At Monday’s press briefing, Transport Minister Hishammuddin Hussein reacted angrily when a foreign journalist suggested Malaysia should apologise for its handling of the crisis.

“That’s purely erroneous. I’ve also got a lot of feedback that, in the circumstances we have been facing, that we have been very responsible in our actions,” he said.

“I think it is very irresponsible of you to say that.”

Twenty-six countries were now involved in searching for the jet after satellite and military radar data projected two dauntingly large corridors the plane might have flown through.

The northern corridor stretches in an arc over south and central Asia, while the other swoops deep into the southern Indian Ocean towards Australia.

Malaysia announced that it was deploying its navy and air force to the southern corridor, where Australian Prime Minister Tony Abbott said his country would take the lead in searching a vast area off its west coast.

Three officials from France’s civil aviation accident investigation agency arrived in Kuala Lumpur on Monday to share their experiences of the search for Air France Flight 447, which crashed in the Atlantic Ocean in 2009.

The “black boxes” from that crash were eventually recovered nearly two years later from a depth of more than 3,800 meters.

The Malaysian authorities have stressed that the backgrounds of all the passengers and crew were being checked, as well as engineers who may have worked on the plane before take-off.

Senior US intelligence officials cited by the New York Times said they had run the names of everyone on board through their data banks without any tangible result.

That included a check on a passenger identified as an artist belonging to China’s Muslim Uighur minority. Uighur separatists have become increasingly militant in their fight against Chinese rule.

Malaysian police have searched both pilots’ residences and are examining a flight simulator that Captain Zaharie, 53, had assembled at his home.

Associates say Zaharie was an active supporter of Malaysia’s political opposition headed by veteran politician Anwar Ibrahim.

In a highly controversial case, Anwar was convicted of sodomy -- illegal in Muslim Malaysia -- just hours before MH370 took off.

But friends said Zaharie exhibited no extreme views.

Fariq, meanwhile, was accused in an Australian television report of allowing two young South African women into the cockpit of a plane he piloted in 2011, breaching security rules imposed after the 9/11 attacks in the United States.

But acquaintances have attested to his good character, and reports said he planned to wed his flight-school sweetheart.

Hishammuddin noted that the two pilots “did not ask to fly together” on flight 370. (AFP)