KUALA LUMPUR, Malaysia Officials revealed a new timeline Monday suggesting the final voice transmission from the cockpit of the missing Malaysian plane may have occurred before any of its communications systems were disabled, adding more uncertainty about who aboard might have been to blame.

The search for Flight 370, which vanished early March 8 while flying from Kuala Lumpur to Beijing with 239 people on board, has now been expanded deep into the northern and southern hemispheres. Australian vessels scoured the southern Indian Ocean and China offered 21 of its satellites to help Malaysia in the unprecedented hunt.

With no wreckage found in one of the most puzzling aviation mysteries of all time, passengers’ relatives have been left in an agonizing limbo.

Investigators say the Boeing 777 was deliberately diverted during its overnight flight and flew off-course for hours. They haven’t ruled out hijacking, sabotage, or pilot suicide, and are checking the backgrounds of the 227 passengers and 12 crew members – as well as the ground crew – for personal problems, psychological issues or links to terrorists.

Malaysian Defense Minister Hishammuddin Hussein said finding the plane was still the main focus, and he did not rule out that it might be discovered intact.

“The fact that there was no distress signal, no ransom notes, no parties claiming responsibility, there is always hope,” Hishammuddin said at a news conference.

Malaysian Airlines CEO Ahmad Jauhari Yahya said an initial investigation indicated that the last words ground controllers heard from the plane – “All right, good night” – were spoken by the co-pilot, Fariq Abdul Hamid. A voice other than that of Fariq or the pilot, Zaharie Ahmad Shah would have been clearest indication yet of something amiss in the cockpit before the flight went off-course.

Malaysian officials said earlier that those words came after one of the jetliner’s data communications systems – the Aircraft Communications Addressing and Reporting System – had been switched off, suggesting the voice from the cockpit may have been trying to deceive ground controllers.

However, Ahmad said that while the last data transmission from ACARS came before that, it was still unclear at what point the system was switched off, making any implications of the timing murkier.

The new information opened the possibility that both ACARS and the plane’s transponders, which make the plane visible to civilian air traffic controllers, were turned off at about the same time. It also suggests that the message delivered from the cockpit could have preceded any of the severed communications.

Turning off a transponder is easy and, in rare instances, there may be good reason to do so in flight – for example, if it were reporting incorrect data.