Boeing investigators are confident that debris found on a remote island in the Indian Ocean comes from a 777 aircraft, according to a source close to the investigation.

An international team of aviation experts is trying to determine if that airplane part comes from Malaysia Airlines Flight 370, a Boeing 777 that disappeared in March 2014 with 239 people on board.

A match might help solve the mystery of what happened to that airplane since no other 777s in the world are unaccounted for, according to the Aviation Safety Network, an online database of flight incidents.

People cleaning a beach found the debris Wednesday on Reunion, a French overseas territory in the western Indian Ocean.

The source said Boeing investigators feel confident the piece comes from a 777 because of photos that have been analyzed and a stenciled number that corresponds to a 777 component. A component number is not the same as a part number, which is generally much longer.

Images of the debris also appear to match schematic drawings for the right wing flaperon from a Boeing 777. A flaperon helps the pilot control the aircraft. It is lightweight and has sealed chambers, making it buoyant.

Despite this confidence, no one is saying the part definitely comes from a 777, much less MH370.

The plane debris will be transported to France on Friday evening, a spokeswoman for the Paris prosecutor’s office said. Agnes Thibault-Lecuivre said the piece will arrive in Paris on Saturday and will be sent to Toulouse, the site of the nearest office of the BEA, the French authority responsible for civil aviation accident investigations.

Finding the debris is a “significant development” in the search for MH370, Australian Deputy Prime Minister Warren Truss said.

New debris, which washed ashore Thursday and appears to resemble remnants of a suitcase, is also part of the investigation, Reunion Island police officials confirmed to CNN.

The flight vanished March 8, 2014, en route to Beijing. So far, no confirmed trace of it has been found, making it one of history’s biggest aviation mysteries and leaving relatives of passengers and crew members uncertain about the fate of their loved ones.

Number might help identify debris

Truss said that there is a number — BB670 — on the wreckage that may help investigators in the identification process. He said it wasn’t a serial or registration number but could be a maintenance number.

Australia is leading the underwater search for the remains of Flight 370 in the southern Indian Ocean, some 2,300 nautical miles (3,700 kilometers) east of Reunion. But Truss said that French and Malaysian authorities will be responsible for establishing whether the debris found off the island came from the missing jetliner.

Australia has offered its help, he said, including asking marine experts to look at photos of the debris to determine whether barnacles on it are “consistent with something that was floating in the oceans for 16 months or more.”

Malaysian authorities said they had dispatched a team of aviation experts to Reunion to investigate the discovery, which they described as “a part identified as a flaperon that could possibly belong to the Boeing 777 aircraft that was MH370.”

The Malaysian Prime Minister said Thursday that the debris is “very likely” from a Boeing 777.

But a statement from the Malaysian Transport Ministry cautioned that “until there is tangible and irrefutable evidence that the flaperon does belong to the missing aircraft, it would be premature to speculate.”

The head of the Australian agency leading the search said he hopes to hear “in the next 24 to 48 hours” definitively whether the debris is from MH370.

Martin Dolan, chief commissioner of the Australian Transport Safety Bureau, told CNN’s “New Day” that if the debris is from a Boeing 777, that effectively would confirm it is from Flight 370.

“Our view is there is no other known source for … a piece of that size and significance,” he said.

Family members wary

If it does turn out to be from Flight 370, the development would reassure Australian officials that they are looking for the rest of the plane in the right area, Truss and Dolan said.

“It’s credible that debris from MH370 could have reached the Reunion Islands by now,” Truss said.

Malaysia Airlines is sending a team of investigators to Paris and a second team to Saint-Denis, Reunion, on Friday, an airline official in Kuala Lumpur, Malaysia, told CNN.

It’s unclear how identification will be made.

Normally identification would be aided by a small serial number plate attached to a flaperon, but the part found on the beach appears to be missing the serial number plate, according to photographs.

Other markings may be found on the part, said Michael Kenney of Universal Asset Management in Tupelo, Mississippi, which buys and sells airplanes and parts.

Family members of those who disappeared on board the jetliner are treating the Reunion discovery with caution after witnessing many false leads in the search.

“We will follow the developments and hope to receive the official confirmation as soon as possible,” a group of Chinese families said in a statement Thursday. “We do not want to hear guarantees of 99% likelihood from certain authorities. We need confirmation of 100% certainty.”

And even if it is from the plane, it will still leave many of the relatives’ questions unanswered.

“No matter where the debris is found, we care more about the whereabouts of our family members,” the Chinese statement said. “Did the plane make a landing at some point? Did all passengers re-board? Nobody has answered those questions.”

‘There are a lot of very wild theories out there’

Confirmation that the object is from the missing plane would put to rest some of the more extreme theories about what happened, Truss told reporters.

“There are a lot of very wild theories out there … that it has landed in Russia or that it has been sighted in places where it is way beyond the range of its fuel,” he said.