(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.
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.