KUALA LUMPUR, Malaysia (AP) -- More than four days after a Malaysian jetliner went missing en route to Beijing, authorities acknowledged Wednesday they didn't know which direction the plane carrying 239 passengers was heading when it disappeared, vastly complicating efforts to find it.
Amid intensifying confusion and occasionally contradictory statements, the country's civil aviation authorities and the military said the plane may have turned back from its last known position between Malaysia and Vietnam, possibly as far as the Strait of Malacca, a busy shipping lane west of Malaysia.
How it might have done this without being clearly detected remains a mystery, raising questions over whether its electrical systems, including transponders allowing it to be identified by radar, were either knocked out or turned off. If it did manage to fly on, it would challenge earlier theories that the plane may have suffered a catastrophic incident, initially thought reasonable because it didn't send out any distress signals.
Vietnamese officials gave conflicting accounts of whether the search effort there was being scaled back as a result of the confusion. This likely will anger relatives of those on board who are desperate for information about the fate of their loved ones.
Authorities have not ruled out any possible cause, including mechanical failure, pilot error, sabotage or terrorism. Both the Boeing 777 and Malaysia Airlines have excellent safety records. Until wreckage or debris is found and examined, it will be very hard to say what happened.
The search for the missing aircraft was begun from the spot it was last reported to be over the ocean between Malaysia and Vietnam. But Malaysian authorities have said search operations were ongoing in the Strait of Malacca. Scores of planes and aircraft have been scouring waters in both locations.
The country's air force chief, Gen. Rodzali Daud, released a statement denying remarks attributed to him in a local media report saying that military radar had managed to track the aircraft turning back from its original course, crossing the country and making it to the Malacca strait. Associated Press contacted a high-level military official, who confirmed the remarks.
Rodzali referred to a statement he said he made March 9 in which he said the air force has "not ruled out the possibility of an air turn back" and said search and rescue efforts had been expanded to the waters around Penang Island, in the northern section of the strait.
"There is a possibility of an air turn back. We are still investigating and looking at the radar readings," the country's civilian aviation chief Azharuddin Abdul Rahman said today.
It is possible that the radar readings are not definitive or subject to interpretation, especially if a plane is malfunctioning.
The confusion has prompted speculation that different arms of the government have different opinions over where the plane is most likely to be, or even that authorities are holding back information. The crisis may have led to internal mix-ups and miscommunication.
The Strait of Malacca that separates Malaysia from Indonesia's Sumatra Island is 400 kilometers (250 miles) from where the plane was last known to have made contact with ground control officials over the Gulf of Thailand at a height of 35,000 feet (almost 11,000 meters) early Saturday
Indonesia air force Col. Umar Fathur said the country had received official information from Malaysian authorities that the plane was above the South China Sea, about 20 kilometers (12 miles) from Kota Bharu, Malaysia, when it turned back toward the strait and then disappeared. That would place its last confirmed position closer to Malaysia than has previously been publicly disclosed.
Fathur said Malaysian authorities have determined four blocks to be searched in the strait, which Indonesia was assisting in.
Vietnam's Deputy Transport Minister Pham Quy Tieu was quoted by the Laborer Newspaper as telling reporters that operations had been scaled down following the air force chief's reported remarks, while Vietnam awaited confirmation. But Lt. Gen. Vo Van Tuan, deputy chief of staff of Vietnamese People's Army, said this was not the case, and that efforts were being intensified. It wasn't immediately possible to clear up the conflicting accounts.
Malaysian Police Chief Khalid Abu Bakar, who has been ordered to look at possible criminal aspects in the disappearance of the plane, said Tuesday that hijacking, sabotage and issues related to the pilots' psychological health were being considered.
Aviation experts said they were becoming more uncertain about what most likely happened to the airliner.
Some said a major power outage was an unlikely explanation for why the aircraft's transponder and communications system were apparently not functioning at the time it was reportedly detected by Malaysian military radar flying back toward Malaysia.
With a power catastrophe so large that the various back-up systems, independent power supplies and built-in redundancies could not cope, the aircraft would be barely able to fly, said Jason Middleton, professor of aviation at the University of New South Wales.
Yet Middleton said if one or more passengers overpowered the pilots to take control of the plane, they would need training to switch off the transponder and other systems to ensure the jet was able to fly undetected.
"It's stretching belief a little bit that someone's going to be capable enough in the (777) to do all that," Middleton said. "It's a very curious outcome, you just can't rule out the possibility that the captain or the first officer have gone crazy," he said.