KUALA LUMPUR/NEW YORK/PARIS (Reuters) - Investigators trying to solve the disappearance without trace of a Malaysia Airlines jetliner face an extremely rare challenge that could hinder their efforts: they lack the powers of a formal air safety investigation.
Four days after Flight MH370 went missing in mid-air with 239 people on board, no nation has stepped forward to initiate and lead an official probe, leaving a formal leadership vacuum that industry experts say appears unprecedented.
Malaysian officials are conducting their own informal investigations, in cooperation with other governments and foreign agencies, but they lack the legal powers that would come with a formal international probe under U.N.-sanctioned rules.
Those powers include the legal rights to take testimony from all witnesses and other parties, the right to have exclusive control over the release of information and the ability to centralize a vast amount of fragmentary evidence.
A senior official familiar with the preliminary Malaysian probe said Malaysian authorities could not yet convene a formal investigation due to a lack of evidence on where - namely, in which national jurisdiction - the Boeing 777-200ER jet crashed.
He said this was not hampering their work, that preliminary investigations had begun and that they were working with their neighbors, U.S. officials and the jet's maker, Boeing.
The Malaysians have begun collecting information from neighboring countries without any problems, including air-traffic control communications and radar data, he said. "There have been no issues in getting that information."
But Southeast Asian waters are rife with territorial disputes, and any decision by Malaysia to unilaterally open a formal investigation under U.N. rules could be seen as a subtle assertion of sovereignty if the crash site turns out to be inside another country's territory.
Without a formal investigative process being convened quickly under rules set out by the International Civil Aviation Organization (ICAO), a U.N. agency, there is a risk that crucial early detective work could be hampered, and potential clues and records lost, air accident experts said.
Witnesses such as cargo handlers, mechanics and company officials might be reluctant to speak to Malaysian investigators who were operating outside a formal ICAO-sanctioned probe which could offer them some protection from law suits, experts said.
"The sole objective of an accident investigation is to prevent future accidents and not to apportion blame or liability," said aviation lawyer Simon Phippard of international legal firm Bird & Bird.
"The international standards attempt to provide a degree of protection, for example from criminal prosecution, for individuals who give statements to the enquiry."
The lack of a formal investigation also means Malaysia does not have exclusive control over the release of information or the ability to centralize fragmentary evidence such as wreckage parts and witness accounts, effectively relying for cooperation on other parties' good-will, the experts said.
Under a formal investigation, a board is set up to designate parties to the investigation, including the plane maker, engine maker, unions, the airline and aviation safety regulatory agency of the country where the airline is based. Each of these parties typically has a representative on each of the working groups.
"If they haven't even decided what country is in charge of the investigation, then whatever is being done at this point is probably suffering from a severe lack of top-down control and coordination," said Ted Ellett, an aviation lawyer at Hogan Lovells in Washington and a former Federal Aviation Administration (FAA) chief counsel.
U.S. investigators from the National Transportation Safety Board (NTSB), FAA and Boeing arrived in Kuala Lumpur on Monday and, according to the official familiar with the Malaysian probe, have been talking with the Malaysian investigators.
An NTSB-led team, including the FAA and Boeing officials, is "standing by for when the aircraft is located and they are in touch with Malaysian officials and have offered our assistance and support for anything they may need," NTSB spokeswoman Kelly Nantel said.
Boeing and FAA declined to comment.
A lack of clarity over the investigation already appears to be a source of tension between Malaysia and China, which had up to 154 citizens on the Beijing-bound flight and is pushing for a significant role in the investigation. China's Foreign Ministry urged Malaysia on Monday to step up its search efforts and start an investigation "as soon as possible and correctly".
The deputy head of China's civil aviation authority urged Malaysia to help a team of investigators it has said is ready to fly to the Southeast Asian nation to help with the probe.
Governments usually step forward quickly after an accident to claim leadership of the investigation, based primarily on the territory where the plane crashed.
That crucial information remains unknown in this case, as navies, military aircraft, coastguard and civilian ships from 10 nations scour a huge swathe of the sea from the South China Sea to the Strait of Malacca off Malaysia's western coast.
The official familiar with the preliminary Malaysian investigation said the Malaysian government could not launch a formal probe until the crash site had been found, and that it planned to work closely with U.S. authorities and Australia.
"If we wait, we will lose precious time. We know that. That is why our guys have been gathering all of the records and data," the official said.
Under U.N. rules, if a plane crashes in international waters, the country where the aircraft is registered - in this case, Malaysia - is in charge of the investigation.
So, for example, Air France quickly took control of the official investigation when its passenger jet crashed in waters far out into the Atlantic Ocean in 2009, even though no wreckage had yet been found.
Vietnam would have jurisdiction if the plane crashed in its territory, but it does not have the resources to lead an investigation and would likely have to get outside help, two regional aviation officials said.
Under rules governed by ICAO, setting up an investigation grants "unhampered access" to all relevant materials including wreckage and data and "unrestricted control" over the evidence and public communications.
"Parties don't relish the idea of their officials or employees being queried or formally interviewed in these accident investigations," Ellett said.
"If there's any question about who has the authority to do it, the parties involved could say we're not going to participate until we know who's really in charge."
With lawsuits potentially swirling, the investigation is meant to encourage witnesses to speak freely about the incident in the interests of airline safety.
Investigators will typically "freeze" documents and records, especially the maintenance records of the aircraft, and acquire radar images and air traffic control recordings. Groups specializing in operations, maintenance and sometimes human factors are set up to sift through each scrap of evidence.
"I can't remember anything like this. Usually it is pretty clear who is responsible for the investigation and they get to work straight away," said one European air safety official, who asked not to be identified.
"It is very important to get all the factual information as soon as possible."
(The story changes dateline to Paris from London; no changes to text)
Additional reporting by Stuart Grudgings in KUALA LUMPUR, Ben Blanchard and Megha Rajagopalan in BEIJING, Mark Hosenball in WASHINGTON.; Writing By Stuart Grudgings; Editing by Mark Bendeich