KUALA LUMPUR, Malaysia — A police investigation may never determine the reason why the Malaysia Airlines jetliner disappeared, and search planes scouring the India Ocean for any sign of its wreckage aren’t certain to find anything either, officials said Wednesday.

The assessment by Malaysian officials underscored the lack of knowledge authorities have about what happened on Flight 370. It also points to a scenario that becomes more likely with every passing day – that the fate of the Boeing 777 and the 239 people on board might remain a mystery forever.

The plane disappeared March 8 on a flight to Beijing from Kuala Lumpur after its transponders, which make the plane visible to commercial radar, were shut off. Military radar picked up the jet just under an hour later, on the other side of the Malay peninsula. Authorities say until then its “movements were consistent with deliberate action by someone on the plane” but have not ruled out anything, including mechanical error.

Police are investigating the pilots and crew for any evidence suggesting they may have hijacked or sabotaged the plane. The backgrounds of the passengers, two-thirds of whom were Chinese, have been checked by local and international investigators and nothing suspicious has been found.

“Investigations may go on and on and on. We have to clear every little thing,” Inspector General Khalid Abu Bakar told reporters in Kuala Lumpur. “At the end of the investigations, we may not even know the real cause. We may not even know the reason for this incident.”

Police are also investigating the cargo and the food served on the plane to eliminate possible poisoning of passengers and crew, he said.

The search for the plane began over the Gulf of Thailand and South China Sea where the plane’s last communications were, and then shifted west to the Strait of Malacca where it was last spotted by military radar. Experts then analyzed hourly satellite “handshakes” between the plane and a satellite and now believe it crashed somewhere in the southern Indian Ocean.

A search there began just over two weeks ago, and now involves at least nine ships and nine planes.

The current search area is an 85,000-square-mile patch of sea roughly a 21/2-hour flight from Perth, Australia. The focus of the search has moved several times as experts try to estimate where the plane is most likely to have landed based on assumptions on its altitude, speed and fuel. Currents in the ocean also are being studied to see where wreckage is most likely to have drifted.