U.S. investigators believe missing Malaysia Airlines Flight 370 may have flown for an additional four hours after it reached final known location, according to a report in the Wall Street Journal. If the reports are true, the plane could have traveled another 2,200 nautical miles, giving it time to reach Pakistan, the Indian Ocean, or the Arabian Sea.

Two officials with knowledge of the U.S.'s investigation told the Journal that aviation investigators and national security officials think the plane flew for a total of five hours, four hours past the one hour estimate initially given after the flight vanished early Saturday morning. Their information is based on flight data automatically sent out from the planes Rolls-Royce engines as part of the planes's maintenance program.

From the Wall Street Journal:

U.S. counterterrorism officials are pursuing the possibility that a pilot or someone else on board the plane may have diverted it toward an undisclosed location after intentionally turning off the jetliner's transponders to avoid radar detection, according to one person tracking the probe.

The investigation remains fluid, and it isn't clear whether investigators have evidence indicating possible terrorism or sabotage. So far, U.S. national security officials have said that nothing specifically points toward terrorism, though they haven't ruled it out.

But the huge uncertainty about where the plane was headed, and why it apparently continued flying so long without working transponders, has raised theories among investigators that the aircraft may have been commandeered for a reason that appears unclear to U.S. authorities. Some of those theories have been laid out to national security officials and senior personnel from various U.S. agencies, according to one person familiar with the matter.

One such theory, reportedly under active pursuit by U.S. investigators, is that the plane was diverted "with the intention of using it later for another purpose."

Meanwhile, the search for debris spotted on Sunday by Chinese satellites has so far turned up empty. "There is nothing. We went there, there is nothing," Malaysia's civil aviation chief Azharuddin Abdul Rahman told reporters in Kuala Lumpur on Thursday.

UPDATE 8:47 am: CNN spoke with Malaysia Airlines Chief Executive Ahmad Jauhari Yahya, who denied the Journal's report. From CNN:

But Malaysia Airlines Chief Executive Ahmad Jauhari Yahya said Thursday that Rolls-Royce and Boeing have reported that they didn't receive transmissions of any kind after 1:07 a.m. Saturday. Air traffic controllers lost contact with the plane shortly afterward, around 1:30 a.m.

Malaysia's acting Transportation Minister Hishammuddin Hussein also rebutted the report, calling it "inaccurate."

[Image via Getty]