No signal had been picked up from a Malaysia Airlines Boeing B777-200 aircraft flight carrying 239 passengers and crew from Kuala Lumpur to Beijing, a Vietnamese rescue official said on Saturday.
"We have been seeking but no signal from the plane yet," Pham Hien, director of a Vietnam maritime search and rescue coordination centre in Vung Tau, told Reuters by telephone.
Vietnamese and Chinese media had reported that a signal from the plane had been picked up. The reports did not identify what kind of signal.
"The information on local media about the signal near the Cape Ca Mau was inaccurate," Pham said.