Malaysia's transport minister says the search for a missing airliner is being expanded westward only because it's still missing, and not because of any new information about the disappearance.

The international search expanded today further into the Indian Ocean amid signs the aircraft may have flown on for hours after its last contact with air-traffic control.

Nearly 600 uninhabited islands will be included in the search for the jetliner.  

India began searching groups of islands covered in dense, tropical jungle today.

U.S. officials think two communications systems on the missing jet shut down at different times.  

A source tells ABC News this indicates the airplane did not experience a catastrophic failure.  

The officials believe the data reporting system was shut down first and the transponder was shut down 14 minutes later.  

Sources say this indicates the systems were deliberately turned off, suggesting a possible hijacking or other unusual event. 

Malaysia Airlines Flight 370 was flying from Kuala Lumpur to Beijing with nearly 240 people on board when it disappeared Saturday.