(CNN) -- Here are the latest developments in the investigation into missing Malaysia Airlines Flight 370.
Malaysian Inspector-General of Police Khalid Abu Bakar announced that investigators had cleared all 227 passengers of any role in a hijacking or sabotage, and of having personal or psychological issues that might have played a role in the plane's March 8 disappearance. And a senior Malaysian government official told CNN last week that authorities have found nothing about either of the pilots to suggest a possible motive.
The case has been criminal investigation since March 16, Khalid said. That corroborates a report from a Malaysian government source who told CNN on Monday that the airliner's turning from its course -- caused either by one of the pilots or by someone else -- was being considered a "criminal act."
Malaysian police have interviewed about 170 people and were planning to continue questioning relatives of the 239 passengers and crew members who were aboard the Boeing 777-200ER, as well as others who may have had access to the plane.
Police have said they were looking at four criminal possibilities: hijacking, sabotage, personal problems and psychological issues.
Mechanical failure has not been ruled out, either.
"We have to clear every little thing"
Police must investigate and clear "every little thing" when it comes to investigating the disappearance of MH370, the inspector-general told reporters after a speech at a police academy in Kuala Lumpur Wednesday.
"We are very detailed in our investigation. You must give us all the time. You cannot hurry us in whatever we are doing," Khalid said.
"Even the food -- who prepares the food for the passengers on the plane -- that also we'll have to look into," he added.
Ramping up security
From CNN's David Fitzpatrick and Shimon Prokupecz in Kuala Lumpur: In light of missing MH370, Malaysia Airlines pilots have received a handout on increased cockpit security. The measures include a rule saying no pilot or first officer will be allowed to remain alone in the cockpit, according to two sources familiar with Malaysia Airlines operations.
Looking for a needle in a haystack would be easier
Up to 10 planes and nine ships searched 85,300 square miles (221,000 square kilometers) of ocean northwest of Perth on Wednesday. The search zone shifted eastward toward the Australian coast from where it had been on Tuesday, the Australian Maritime Safety Authority said.
"They are looking in a vast area in very deep waters ... and we really have no idea where it went in," said Bill Schofield, an Australian scientist who helped create the flight data recorders that, if found, could prove key to the investigation.
"A needle in a haystack would be much easier to find."
More assets are streaming in to aid in the search, including high-tech gadgets.
The HMS Tireless, a British nuclear submarine, will take part. It will be joined by an Australian navy ship equipped with a pinger locator designed to listen for beacons attached to the plane's flight data recorder, plus a submersible that can search the ocean floor for wreckage.
But the equipment won't be of use until wreckage from the plane is found and the search zone narrowed. That's because neither the pinger locator nor the submersible -- both of which are from the U.S. Navy -- can quickly scan the enormous area being searched.
"We answered all their questions"
Of those aboard, 154 were Chinese nationals.
On Wednesday, families of 18 Chinese passengers met privately for three hours with Malaysian government officials and investigators in Kuala Lumpur. The meeting had been called after the family members accused Malaysia of not being up-front with them about the investigation.
"We had a very good meeting with them," Azharuddin Abdul Rahman, head of Malaysia's civil aviation department, said after the information session with the families. "We answered all their questions."
The families' representative saw it differently: "I personally believe today's meeting had some progress, but the time was short and family members didn't have an opportunity to raise questions," said Jiang Hui.
Jiang said the families saw new data and PowerPoint slides that hadn't been shared before -- but the flight tracks were not provided.
Malaysian authorities said this week that the last voice transmission from the cockpit was not "All right, good night," as they had previously said, but "Good night Malaysian three-seven-zero."
While the difference may appear inconsequential, the fact that authorities gave an incorrect version and let it stand for weeks undermines the public's confidence in the investigation, air accident investigation experts told CNN.
"High criticism is in order at this point," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation.
Malaysian PM heads to Perth
According to Wednesday's Transport Ministry statement, Prime Minister Najib Razak is due to land at Perth Airport at approximately 11 p.m. Wednesday (11 a.m. ET). He's scheduled to visit Pearce Air Force base on Thursday morning "to meet with personnel involved in the multinational search operation for MH370. The Prime Minister will also be briefed on the latest developments regarding the search." He'll also participate in a bilateral meeting with Australian Prime Minister Tony Abbot.
For those keeping count ...
There have been at least six missteps in Malaysia Flight 370 investigation. Here's a look at each one.
There's a Peter Jackson angle
Radio New Zealand, citing a spokesperson, reports that "Lord of the Rings" filmmaker Peter Jackson's private jet is being used to assist in the international search effort. Jackson's manager told CNN Wednesday that Wingnut Films, Jackson's production company, has privately chartered an aircraft "in this instance," but would not comment further.