* Malaysia says has sent team to Reunion Island
* French authorities say "ruling nothing out"
* Australia says number on debris could speed verification
* Currents could have pushed debris far from crash site - experts
* MH370 disappeared without a trace in March 2014
By Joe Brock
SAINT-DENIS, Reunion, July 30 (Reuters) - Malaysia is "almost certain" plane debris washed up on the Indian Ocean island of Reunion is part of a Boeing 777, its deputy transport minister said, heightening the possibility it could be wreckage from missing Flight MH370.
The object, which appears to be part of a wing, was being sent to a French military laboratory near Toulouse to verify if it is indeed the first trace of the lost plane to be found, police sources said.
Malaysian air investigators are due in Reunion on Friday.
National carrier Malaysia Airlines was operating a Boeing 777 on the ill-fated flight, which vanished in March last year en route from Kuala Lumpur to Beijing in one of the most baffling mysteries in aviation history.
It was carrying 239 passengers and crew.
Search efforts led by Australia have focused on a broad expanse of the southern Indian Ocean off Australia. Reunion Island, where the debris was found washed up on Wednesday, is a French overseas department roughly 3,700 km (2,300 miles) away,
"The location is consistent with the drift analysis provided to the Malaysian investigation team, which showed a route from the southern Indian Ocean to Africa," Malaysian Prime Minister Najib Razak said in a statement.
There have been four serious accidents involving 777s in the 20 years since the widebody jet came into service. Only MH370 is thought to have crashed south of the equator.
"No hypothesis can be ruled out, including that it would come from a Boeing 777," the Reunion prefecture and the French Justice Ministry said in a joint statement.
Reunion, a volcanic island of just 850,000 people 600 km (370 miles) east of Madagascar, has seldom known such attention.
"It's incredible," said Marie-Noelle Le Nivet, a 49-year-old management consultant. "Our lovely beautiful little island and the whole world is watching. It's amazing."
Aviation experts who have seen widely circulated pictures of the debris said it may be a moving wing surface known as a flaperon, situated close to the fuselage.
"It is almost certain that the flaperon is from a Boeing 777 aircraft. Our chief investigator here told me this," Malaysian Deputy Transport Minister Abdul Aziz Kaprawi told Reuters.
Australia's Deputy Prime Minister Warren Truss said a number stamped on the 2-2.5 metres (6.5-8 ft) chunk of debris might speed up its verification.
"This kind of work is obviously going to take some time although the number may help to identify the aircraft parts, assuming that's what they are, much more quickly than might otherwise be the case," he said.
Investigators believe someone deliberately switched off MH370's transponder before diverting it thousands of miles off course. Most of the passengers were Chinese. Beijing said it was following developments closely.
For the families of those on board, lingering uncertainty surrounding the fate of the plane has been agony.
"Even if we find out that this piece of debris belongs to MH370, there is no way to prove that our people were with that plane," said Jiang Hui, 41, whose father was on the flight.
Zhang Qihuai, a lawyer representing some of the passengers' families, said a group of around 30 relatives had agreed they would proceed with a lawsuit against the airline if the debris was confirmed to be from MH370.
According to photographs, the piece of debris is fairly intact and with no burn marks or signs of impact. Flaperons help pilots control an aircraft while in flight.
Greg Feith, an aviation safety consultant and former crash investigator at the U.S. National Transportation Safety Board (NTSB), said his sources at Boeing had told him the piece was from a 777. Whether it was MH370 was not clear, he said.
"But we haven't lost any other 777s in that part of the world," Feith said.
Boeing declined to comment on the photos.
Oceanographers said vast, rotating currents sweeping the southern Indian Ocean could have deposited wreckage from MH370 thousands of kilometres from where the plane is thought to have crashed.
If confirmed to be from MH370, experts will try to retrace the debris drift back to its source. But they caution that the discovery was unlikely to provide any more precise information about the aircraft's final resting place.
"This wreckage has been in the water - if it is MH370 - for well over a year so it could have moved so far that it's not going to be that helpful in pinpointing precisely where the aircraft is," Australia's Truss told reporters.
Robin Robertson, an oceanographer at the University of New South Wales in Sydney, said the timing and location of the debris made it "very plausible" that it came from MH370, given what was known about Indian Ocean currents.
Aviation consultant Feith said that if the part was from MH370, the bulk of the plane likely sank, while the flaperon had air pockets that allowed it to float below the water's surface.
Finding the wreckage would involve reverse engineering the ocean currents over 18 months, Feith said. "It's going to take a lot of math and science to figure that out," he said. (Reporting by Tim Hepher, Emmanuel Jarry and Matthias Blamont in PARIS, Lincoln Feast and Swati Pandey in SYDNEY, Alwyn Scott in NEW YORK, Siva Govindasamy in SINGAPORE, Sui Lee Wee in BEIJING and Praveen Menon in KUALA LUMPUR; Writing by Dean Yates; Editing by Alex Richardson, Paul Tait and Giles Elgood)