In what represents yet another new theory, military radar data is suggesting that a Malaysia Airlines jetliner missing for nearly a week was deliberately flown hundreds of miles off course.

As the search for the missing Boeing 777 continues nearly a week after it vanished with 239 people on board, sources familiar with the investigation have said analysis of the Malaysian data suggests the plane was deliberately flown towards the Andaman Islands.

Two sources told Reuters an unidentified aircraft that investigators believe was Flight MH370 was following a route between navigational waypoints when it was last plotted on military radar off the country’s northwest coast.

This indicates that it was either being flown by the pilots or someone with knowledge of those waypoints, the sources said.

The last plot on the military radar's tracking suggested the plane was flying toward India's Andaman Islands, a chain of isles between the Andaman Sea and the Bay of Bengal, they said.

Waypoints are geographic locations, worked out by calculating longitude and latitude, that help pilots navigate along established air corridors.

A third source familiar with the investigation said inquiries were focusing increasingly on the theory that someone who knew how to fly a plane deliberately diverted the flight.

“What we can say is we are looking at sabotage, with hijack still on the cards,” said that source, a senior Malaysian police official.

All three sources declined to be identified because they were not authorised to speak to the media and due to the sensitivity of the investigation.

Officials at Malaysia’s Ministry of Transport, the official point of contact for information on the investigation, did not return calls seeking comment.

Malaysian police have previously said they were investigating whether any passengers or crew had personal or psychological problems that might shed light on the mystery, along with the possibility of a hijacking, sabotage or mechanical failure.

As a result of the new evidence, the sources said, multinational search efforts were being stepped up in the Andaman Sea and also the Indian Ocean.

As one of the most baffling mysteries in the history of modern aviation remains unsolved after nearly a week, the latest radar evidence is consistent with the expansion of the search for the aircraft to the west of Malaysia.

There has been no trace of the plane nor any sign of wreckage as the navies and military aircraft of more than a dozen countries scour the seas across Southeast Asia.

Indian ships and planes have been searching northwest of Malaysia in the eastern Andaman Sea, and on Friday expanded their search to areas west of the Andaman and Nicobar Islands chain Friday, said V.S.R. Murty, an Indian Coast Guard inspector-general.

The White House said the U.S. may be drawn into a new phase of the search in the vast Indian Ocean but did not offer details. The U.S. Navy 7th Fleet said it was moving one of its ships, the USS Kidd, into the Strait of Malacca.

“It’s my understanding that based on some new information that’s not necessarily conclusive – but new information – an additional search area may be opened in the Indian Ocean,” White House spokesman Jay Carney told reporters in Washington.

Carney did not specify the nature of the new information.

A statement from Malaysia’s ministry of transport said it was following all leads that might help locate the aircraft.

Satellites picked up faint electronic pulses from the aircraft after it went missing on Saturday, but the signals gave no immediate information about where the jet was heading and little else about its fate, two sources close to the investigation said on Thursday.

U.S. experts are still examining the data to see if any information about its last location could be extracted, a source close to the investigation told Reuters.

The ‘pings’ indicated its maintenance troubleshooting systems were switched on and ready to communicate with satellites, showing the aircraft was at least capable of communicating after losing touch with 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, they said.

In one of the most baffling mysteries in modern aviation, no trace of the plane nor any sign of wreckage has been found despite a search by the navies and military aircraft of more than a dozen countries.

•Excerpted from MailOnline. Photo shows one of the crews searching for the missing plane.