Investigators have cleared all passengers on Malaysia Airlines Flight 370 of any role in hijacking or sabotage or of having personal or psychological issues that could have played a role in the plane's disappearance, the inspector general of police, Khalid Abu Bakar, said Wednesday

The investigation into what happened to Malaysia Airlines Flight 370 is charging ahead on two fronts: new high-tech tools and old-fashioned police work.

While searchers scanned the ocean surface for a 26th day Wednesday with planes and ships, the possibility that something sinister may have happened hasn't been discounted.

Malaysian police said Wednesday they have interviewed about 170 people, and will continue questioning families and those who had access to the plane.

Officials have always said they were looking at four possibilities: hijacking, sabotage, personal problems and psychological issues.

A Malaysian government source told CNN on Monday that the airliner's turn off course is being considered a "criminal act," either by one of the pilots or someone else.

But a senior Malaysian government official told CNN last week that authorities have found nothing in days of investigating the two pilots that leads them to any motive, be it political, suicidal or extremist.

On Wednesday, CNN learned that Malaysia Airlines pilots have received a handout on increased cockpit security, according to two sources familiar with the airlines' operations.

The measures include a rule saying no pilot or first officer will be allowed to sit alone in the cockpit. If one or the other leaves the cockpit, a senior cabin steward must remain inside the cockpit until the pilot or first officer returns.

"These changes are positive in nature and directly relate to the MH 370 incident," one of the sources told CNN.

The flight simulator in the pilot's house is still inconclusive, police said Wednesday. Authorities are awaiting an expert's report.

"It's one of the great mysteries of our time," Australian Prime Minister Tony Abbott said in a radio interview from Perth, where he'll host his Malaysian counterpart Najib Razak later Wednesday.

"We owe it to the world, we owe it to those families to do whatever we reasonably can do get to the bottom of this."(CNN)