马航班机在失联后数小时内向卫星发送电子脉冲信号

The search for a missing Malaysian jetliner expanded toward the Indian Ocean on Friday, as new evidence emerged that the jet may have traveled for hours after it vanished.

Speaking anonymously, U.S. officials briefed on the investigation said the Boeing 777 sent automated electronic messages to satellites several hours after it disappeared from civilian radar Saturday.

The officials said the communications satellites detected faint messages, known as pings, which attempted to relay regular maintenance and other data about the plane's condition.

It is not clear whether the messages can provide information on the plane's location. It is also not clear whether the plane was in the air at the time the messages were sent.

Ships and planes from over a dozen countries have been searching for six days for the Malaysia Airlines plane and its 239 people on board, who were headed from Kuala Lumpur to Beijing.

The initial search focused on the Gulf of Thailand, where the airliner was last spotted by civilian radar. The Malaysian military has since said it may have tracked the plane hundreds of kilometers away, across the Malaysian peninsula in the Strait of Malacca.

On Thursday, White House spokesman Jay Carney said "an additional search area may be opened" in the vast Indian Ocean. It is the world's third largest ocean and is significantly deeper than the other search areas.