Lost Malaysia plane 'may have flown on for five hours'
The missing Malaysia Airlines flight MH370 may have been flying for more than five hours after it disappeared, the BBC has learned.
It is believed the plane was sending automated signals to a satellite system long after radar contact was lost.
On Friday, US surveillance teams were sent to the Indian Ocean, much further west than the initial searches.
The Indian navy has also been asked to search an area in the Bay of Bengal off India's Chennai coast.
Flight MH370 vanished last Saturday with 239 people on board.
The plane - which was supposed to be flying to Beijing from Kuala Lumpur - last made contact with air traffic control over the South China Sea to the east of Malaysia.
However, the BBC understands that a satellite system operated by London-based telecommunications company Inmarsat received an automated signal from flight MH370 at least five hours after the plane was reported lost.
BBC science correspondent Jonathan Amos says the signal could only have been sent if the plane was intact and powered, and may explain why search teams have moved to the Indian Ocean.
Earlier, US media outlets also quoted unnamed officials as saying that the Boeing 777 was "pinging" satellites for hours after its last contact with air traffic controllers.
That led searchers to believe the plane could have flown more than 1,600 km (1,000 miles) beyond its last confirmed radar sighting.
White House spokesman Jay Carney has confirmed that US teams were shifting their focus to the Indian Ocean because of "new information", but gave no further details.
Malaysia has not yet commented on the latest claims.
The US - one of a number of countries helping to search for the plane - has sent a navy destroyer and a sophisticated surveillance aircraft to the Indian Ocean.
The Indian navy, air force and coast guard are also now involved after a request from the Malaysian government.
Indian naval spokesman DK Sharma said on Friday that six ships and five aircraft were scouring the Andaman Sea.
Malaysian authorities later said that India's Eastern Naval Command was to search an area of sea 9,000 sq km (3,500 sq miles) off the Chennai coast
The BBC's Jonathan Head in Kuala Lumpur says the latest claims are being taken seriously by the US.
However, he cautions that there have already been a number of false leads.
As the search continues, families of those on board are enduring an agonising wait for news.
Feng Zhiliang, whose cousin Feng Dong, 21, was a passenger, told the BBC in Beijing that families had spent the past week "in agony and desperation".
"It's been a time of extreme emotions, real ups and downs. We are very disappointed with the response of the Malaysian authorities. The information they give out is completely contradictory."
He added: "Until it's clear what happened we still have hope that our families will return home safely."
Malaysia's acting Transport Minister Hishammuddin Hussein said that the search area was expanding both east and west of the Malaysian peninsula.
He said he was aware of the claims about satellite data, but he would not comment unless the information had been "corroborated by the relevant authorities".
China said on Friday it was sending a patrol ship to the Malacca Strait, west of Malaysia, after a fruitless search in the Gulf in Thailand.
The official Xinhua news agency said experts and officials had met on Friday and "analysed new information", but did not give details.
Some 153 of the passengers on board the plane were Chinese, and Beijing has been pressing Malaysia to intensify its search.
Earlier this week, Chinese officials released satellite pictures of debris in the South China Sea.
Mr Hussein later said the images were not connected to flight MH370's disappearance.
But Chinese state TV said a warship was continuing to search for the debris.