SYDNEY — (CNN) The discovery of debris off the coast of Reunion Island is “a very significant development” in the search for Malaysia Airlines Flight 370, but it’s too soon to say whether it’s part of the missing aircraft, Australian Deputy Prime Minister Warren Truss said Thursday.

Authorities are treating it as “a major lead,” Truss told reporters.

The debris was found Wednesday off the coast of Reunion, a French department in the western Indian Ocean. It is being examined to determine whether it is connected to Flight 370, according to a member of the French air force in Reunion.

The passenger jet, a Boeing 777, vanished en route to Beijing in March 2014 with 239 people aboard.

So far, no confirmed trace of it has been found, making it one of history’s biggest aviation mysteries and leaving many relatives of passengers and crew members feeling trapped in uncertainty about the fate of their loved ones.

A source close to the investigation told CNN that Boeing officials believe they are seeing a wing component of a 777 aircraft in the photos of the debris from Reunion.

Truss said Thursday 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 eastern Indian Ocean. But Truss said that French and Malaysian authorities will be responsible for establishing whether the debris found off Reunion came from the jetliner.

The Malaysian government has dispatched a team to Reunion Island to investigate the discovery, Malaysian Minister of Transportation Liow Tiong Lai said in New York on Wednesday.

“We have wreckage found that needs to be further verified before we can further confirm if it belongs to MH370,” the minister said.

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 said.

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

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 previously.

“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.”

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

Malaysia Airlines said it was working with authorities to determine where the part came from.

“At the moment, it would be too premature for the airline to speculate on the origin of the flaperon,” the carrier said, referring to the wing component that the object resembles.

CNN analysts said there are indications the part could be from a Boeing 777, and if that’s the case, it’s likely from MH370.

“If it is a part from a triple 7, we can be fairly confident it is from 370 because there just haven’t been that many triple 7 crashes and there haven’t been any in this area,” said CNN aviation analyst Mary Schiavo.

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