Investigators are trying to determine whether a missing Malaysia Airlines jetliner may have turned back before it went missing.
Radar data suggests Flight MH370 may have tried to go back toward Kuala Lumpur, Malaysian military officials said Sunday. Malaysian air traffic controllers lost contact with the Boeing 777 early Saturday as it traveled from Kuala Lumpur to Beijing.
However, officials said the pilot appears to have given no signal to authorities about the possible change in course," the officials said.
Friends and family continue the agonizing wait to learn the fate of their loved ones on the missing Malaysia Airlines plane. There are 239 people onboard, including 227 passengers and 12 crew members. More than half are Chinese nationals, and at least three passengers are reportedly American.
According to Vietnamese and Chinese state media, the Vietnamese Navy confirmed Flight MH370 has crashed off the southern coast of Vietnam. Oil slicks found in the ocean near the search area are suspected to be from the missing plane, according to the Vietnam government's official news agency. However, Malaysia's acting transport minister says he has received no information on plane wreckage or confirmation of a crash.
To add to the mystery of the plane's disappearance, some people who were supposed to be onboard the flight have turned up alive.
An Austrian citizen, whose name was on the manifest, said he was safe and sound and his passport was stolen two years ago. Authorities in Italy said a man who was also listed on the manifest had his passport stolen last year.
A U.S. official said authorities are aware of reporting about lost or stolen passports used by passengers on the missing flight.
"No nexus to terrorism yet," the official said, "although that's by no means definitive. We're still tracking."
Search and rescue efforts are under way for the aircraft. Malaysia Airlines operates in Southeast Asia, East Asia, South Asia, the Middle East and the route between Europe and Australia.
CNN Wires contributed to this report