(CNN) -- Investigators looking at the flight simulator taken from the home of Malaysia Airlines Flight 370 Captain Zaharie Ahmad Shah have discovered that some data had been erased from it, Malaysia's acting transportation minister said Wednesday.
Hishammuddin Hussein didn't say what had been deleted, but simulation programs typically store data from previous sessions for later playback. He also did not say who might have deleted the data.
The deletions are not necessarily evidence of ill intent: Removing files from a computer is usually an innocent act repeated millions of times a day around the world.
But experts consulted by CNN said it's relatively unusual to delete such data from a simulator: The files are extremely small and are often kept by desktop pilots to gauge their progress, said Jay Leboff, owner of HotSeat, a simulator manufacturer.
"It would be suspicious to me, because there's no need to do it," he said.
Experts are examining the simulator in hopes of recovering the deleted data, Hishammuddin said.
The revelation came as the search for the missing airliner neared its 13th day.
Although the search area spans a vast area of nearly 3 million square miles, a U.S. government official familiar with the investigation said the plane is most likely somewhere on the southern end of the search area.
"This is an area out of normal shipping lanes, out of any commercial flight patterns, with few fishing boats, and there are no islands," the official said, warning that the search could well last "weeks and not days."
The official's comments echo earlier analysis by U.S. officials saying the most likely location for the missing aircraft is on the bottom of the Indian Ocean.
Australia said Wednesday that the area of the southern Indian Ocean where it is searching for the plane has been "significantly refined."
The new area is based on work done by the U.S. National Transportation Safety Board on "the fuel reserves of the aircraft and how far it could have flown," said John Young of the Australian Maritime Safety Authority.
But Australian ships and aircraft have so far seen nothing connected to the missing plane, Australian authorities said.
The lack of progress has angered and frustrated families, who have accused Malaysian officials of withholding information.
Some family members staged a protest at the hotel where media covering the search are staying.
"We have been here for 10 days, no single piece of information," one woman said. "We need media from the entire world (to) help us find our lost families, and find the MH370 plane."
Malaysian authorities appeared to hustle the women away.
In a statement, Hishammuddin said Malaysian authorities "regret the scenes at this afternoon's press conference."
"One can only imagine the anguish they are going through," he said of the families. "Malaysia is doing everything in its power to find MH370 and hopefully bring some degree of closure for those whose family members are missing."
An abrupt change in direction
The plane's disappearance continues to intrigue the public and frustrate officials, who have turned up no sign of the plane despite the involvement of teams from 26 nations.
On Tuesday, a law enforcement official told CNN that the aircraft's first major change of course -- an abrupt westward turn that took the plane off its route to China and back across the Malay Peninsula -- was almost certainly programmed by somebody in the cockpit.
The change was entered into the plane's system at least 12 minutes before a person in the cockpit, believed to be the co-pilot, signed off to air traffic controllers.
Some experts said the change in direction could have been part of an alternate flight plan programmed in advance in case of emergency; others suggested it could show something more nefarious was afoot.
But Hishammuddin said Wednesday that "there is no additional waypoint on MH370's documented flight plan, which depicts normal routing all the way to Beijing."
The Thai military, meanwhile, said it had spotted the plane turning west toward the Strait of Malacca early on March 8. That supports the analysis of Malaysian military radar that has the plane flying out over the Strait of Malacca and into the Indian Ocean.
But it didn't make it any clearer where the plane went next. Authorities say information from satellites suggests the plane kept flying for about six hours after it was last detected by Malaysian military radar.
Malaysian authorities, who are coordinating the search, say the available evidence suggests the missing plane flew off course in a deliberate act by someone who knew what they were doing.
Investigators are looking into the background of all 239 passengers and crew members on board the plane, as well as its ground crew, Malaysian officials have said. They've received background checks on all nations with passengers on board with the exception of Russia and Ukraine, Hussein said.
So far, no information of significance has been found about any passengers, Hishammuddin said.
China says it has found nothing suspicious during background checks on its citizens on the flight -- a large majority of the plane's passengers.
Particular attention has focused on the pilot and first officer on Flight 370, but authorities are yet to come up with any evidence explaining why either of them would have taken the jetliner off course.
And some experts have warned against hastily jumping to conclusions about the role of the pilots.
"I've worked on many cases were the pilots were suspect, and it turned out to be a mechanical and horrible problem," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation. "And I have a saying myself: Sometimes, an erratic flight path is heroism, not terrorism."
Searchers are racing the clock in their efforts to find the plane and its flight-data and cockpit-voice recorders. The devices have batteries designed to send out pings for 30 days. That leaves 18 days until the batteries are expected to run out.
Investigators hope the recorders may reveal vital information about why the passenger jet disappeared.
"The odds of finding the pinger are very slim," said Rob McCallum, an ocean search specialist. "Even when you know roughly where the target is, it can be very tricky to find the pinger. They have a very limited range."
Searchers face deep ocean
Hishammuddin, Malaysia's public face of the search efforts, has repeatedly said that little is likely to be established about the mysterious flight until the plane is found.
But in the Indian Ocean, where Australia and Indonesia have taken the lead in the hunt, some of the depths that searchers are dealing with are significant.
The Bay of Bengal, for example, which lies between Myanmar and India, has depths of between about 4,000 and 7,000 meters (13,000 feet and 23,000 feet), according to McCallum.
Wreckage and bodies of passengers from Air France Flight 447, which crashed into the Atlantic Ocean in 2009, were found at depths of around 12,000 feet by unmanned submarines.
It took four searches over the course of nearly two years to locate the bulk of the wreckage and the majority of the bodies of the 228 people on board Flight 447. It took even longer to establish the cause of the disaster.
Right now, authorities don't even know for sure if the missing Malaysian plane crashed or landed -- or where.
CNN has talked to more than half a dozen U.S. military and intelligence officials who emphasize that while no one knows what happened to the plane, it is more logical to conclude it crashed into the Indian Ocean.
CNN's Brian Todd, David Fitzpatrick, Kyung Lah, Mitra Mobasherat, Atika Shubert, Evan Perez, Mariano Castillo and Catherine E. Shoichet contributed to this report.