Saint-Denis, Reunion Island (CNN)The discovery of debris on a remote island in the Indian Ocean is "a very significant development" in the search for Malaysia Airlines Flight 370, but it's too soon to say whether the part is from the missing aircraft, Australian Deputy Prime Minister Warren Truss said Thursday.
Authorities are treating it as "a major lead," Truss told reporters.
MH370 is the only Boeing 777 that crashed over water and is unaccounted for, according to the Aviation Safety Network, an online database of flight incidents.
The debris was found Wednesday on the beach in Reunion, a French overseas territory 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.
Number might help identify debris
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 southern Indian Ocean, some 2,300 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 nonetheless 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 Island 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."
A flaperon is a lightweight part of an aircraft wing that helps control the plane's movement.
Malaysian Prime Minister Najib Razak said Thursday that the debris is "very likely" from a Boeing 777.
But the 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 Thursday that 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.
It's not clear where the plane part will be examined.
Razak said Thursday that French authorities would ship the part to Toulouse, France, the site of the nearest office of the BEA, the French authority responsible for civil aviation accident investigations.
But also Thursday, the BEA refused to confirm to CNN that the debris would be sent to Toulouse. The agency said any decision to move the debris will be taken by the local gendarmerie, which come under France's Ministry of Justice.
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."
'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 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. It also warned that it was too soon "to speculate on the origin of the flaperon."
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.