KUALA LUMPUR/WASHINGTON (REUTERS) - Satellites picked up faint electronic pulses from Malaysia Airlines flight MH370 after it went missing on Saturday, but the signals gave no information about where the stray jet was heading and little else about its fate, two sources close to the investigation said on Thursday.

But the "pings" indicated that the aircraft's maintenance troubleshooting systems were switched on and ready to communicate with satellites, showing the aircraft, with 239 people on board, was at least capable of communicating after the jet lost touch with Malaysian air traffic controllers.

The system transmits such pings about once an hour, according to the sources, who said five or six were heard.

However, the pings alone are not proof that the plane was in the air or on the ground, the sources said.

An international search is under way over a vast area in the Gulf of Thailand, the Andaman Sea and on both sides of the Malay Peninsula. The United States, which has sent ships and planes, said the area may be expanding into the Indian Ocean.

The area being searched is now the size of Hungary.

The new information shed little light on the mystery of what happened to the plane, whether there was a technical failure, a hijacking or another kind of incident on board after it took off from Kuala Lumpur en route to Beijing.

While the troubleshooting systems were functioning, no data links were opened, the sources said, because the companies involved had not subscribed to that level of service from the satellite operator, the sources said.

Boeing Co, which made the missing 777 airliner, and Rolls-Royce, which supplied its Trent engines, declined to comment.

Earlier Malaysian officials denied reports that the aircraft had continued to send technical data and said there was no evidence that it flew for hours after losing contact with air traffic controllers early Saturday.

The Wall Street Journal had reported that U.S. aviation investigators and national security officials believed the Boeing 777 flew for a total of five hours, based on data automatically downloaded and sent to the ground from its engines as part of a standard monitoring program.

Malaysian authorities have said the last civilian contact occurred as the Boeing 777-200ER flew north into the Gulf of Thailand. They said military radar sightings indicated the plane may have turned sharply to the west and crossed the Malay Peninsula toward the Andaman Sea.