MH370 Probe: Part Number on Debris from Indian Ocean Consistent With 777, Official Says

— -- The piece of an airplane that washed ashore on a small French island near Madagascar yesterday appears to come from a 777, Boeing engineers believe, because of a part number in a photo of the wreckage, a U.S. official familiar with the investigation into told ABC News.

Investigators are treating the debris as a major lead in the search for Malaysia Airlines Flight 370, the Boeing 777 that disappeared last March, the Australian deputy prime minister said today.

Warren Truss called finding the debris, which Malaysia Airlines identified as a flaperon, the first real evidence that a piece of the plane had been discovered.

MH370 vanished on March 8, 2014, with 239 people on board, all of whom are presumed dead.

"If it entered the Indian Ocean in the place where a current search operations are being undertaken, [it] could have reached the Reunion Islands in the 16 months since," he said. "It's the first real evidence that there is a possibility that a part of the aircraft may have been found."

A tattered suitcase also washed ashore today near where the airplane debris was found, according to a newspaper in Reunion Island. Police seized the suitcase as part of its investigation, reports the paper.

Truss said marine researchers have been asked to examine the photographs of the debris to assess whether barnacles seen on the flaperon are consistent with something that was floating in the ocean for more than a year.

"Clearly, we are treating this as a major lead," he said.

While identifying the debris as part of the missing plane won't make it easier to find, Truss said it would help put some of the theories about the flight to bed.

"There are a lot of very wild theories that have been around, including it landed in Russia," he said. "It won't positively prove it is in any other location other than I guess the Indian Ocean."

Truss added that he hoped identifying the debris would bring some closure to the families of those on board the flight.

"If this wreckage [is] from MH370, it's an important breakthrough, particularly for families," he said. "The families who have been involved with this long, long, long, long wait, for them to have some degree of closure would be great comfort."

The debris appeared to be from the same plane as MH370, a Boeing 777, a source familiar with the investigation told ABC News.

Malaysian authorities said a team was headed to Reunion Island to determine whether the debris belonged to MH370. The Malaysians were also in touch with the French's air crash investigation agency.

Former NTSB aviation safety official and current ABC News consultant Tom Haueter said investigators would likely try to match serial numbers found on the flaperon with those from MH370.

"If it is a 777 part, it’s most likely from MH370," he said.

Get real-time updates as this story unfolds. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here.