Malaysia’s handling of the discovery of a wing part that apparently came from the missing Malaysia Airlines Flight 370 has worsened frictions with its partners in the investigation, rekindled frustrations among the families of people who were aboard the plane and further dented the country’s battered credibility.
Many questioned the timing and motives of the Malaysian prime minister, Najib Razak, who announced in the early hours of Thursday that the wing part had been “conclusively confirmed” to be from the missing plane. He spoke just before a news conference in Paris at which French investigators were much more guarded, saying only that the experts had “very strong presumptions” that the part came from the plane, a Boeing 777.
Later on Thursday the Malaysian transportation minister, Liow Tiong Lai, clouded the picture further when he told reporters in Kuala Lumpur that a Malaysian team had found more aircraft debris on the French island of Réunion, where the wing part was discovered last week. The French authorities in Paris denied that any new aircraft debris had been found.
The discrepancies between the Malaysian declarations and what others involved in the investigation, including experts from Boeing, were prepared to conclude about the evidence have created significant tensions between Malaysian and French officials, according to a person close to the investigation.
Mr. Najib has domestic political worries, not least a scandal swirling around a troubled state investment fund that has put him under intense scrutiny. The Wall Street Journal and The Sarawak Report, a website based in Britain, have reported that documents found by investigators in Malaysia indicate that almost $700 million was transferred to accounts that Mr. Najib is believed to control.
In late July, Mr. Najib dismissed his deputy prime minister, who had publicly called on him to give a full account of the matter, and the country’s attorney general, who was one of the leaders of the investigation into the scandal.
But exasperation with the Malaysian authorities dates to when the plane first disappeared, on a night flight from Kuala Lumpur bound for Beijing in the early hours of March 8, 2014. Ground controllers lost contact with the plane about 40 minutes after takeoff, but the authorities did not issue an alert about the missing plane for hours.
Then, Malaysia spent a full week directing a major search-and-rescue effort focused on the Gulf of Thailand, along the plane’s scheduled flight path, even though the Malaysian military had tracked an unidentified aircraft flying in nearly the opposite direction — westward and out into the Indian Ocean — which investigators later concluded was Flight 370.
Eventually, based on the radar data and automated satellite signals received from the jet, investigators concluded that it had flown on for hours more, and probably ran out of fuel and crashed in the Indian Ocean west or southwest of Australia. Searchers began working from the air, and later scanning the deep ocean floor with sonar devices, but nothing has been found there.
The wing part was the first tangible trace of the plane to turn up.
For many people who had loved ones aboard Flight 370, the identification, or near-identification, of the object only intensified their desire to know how and why the jet had veered off course and flown unnoticed into remote ocean waters.
Chinese citizens made up about two-thirds of the 239 people on the plane, and in Beijing, relatives of the victims viewed Mr. Najib’s announcement with skepticism or outright disbelief.
On Thursday morning, about 20 relatives gathered outside the Malaysia Airlines office in Beijing, demanding to talk to airline representatives and to be flown to Réunion. More than two dozen police officers kept them from entering the office building.
“We don’t accept this; this is not closure,” said Dai Shuqing, who had five relatives on the plane, including her sister. “The Malaysians want to lie to the whole world, but they cannot lie to us. We will persevere and keep digging.”
Others outside the airline’s office held signs with slogans such as “Malaysia hides the truth.” Later in the day, some of the relatives moved the demonstration to Boeing’s offices in the city.
Under international aviation conventions, Malaysia is leading the overall Flight 370 investigation because the aircraft was registered in Malaysia and took off from Kuala Lumpur. The ocean search is being led by Australia, whose ports are nearest the search area. But the wing part found on Réunion is being examined at a laboratory near Toulouse, France, because it washed ashore on French territory. The Paris prosecutor’s office has opened an inquiry into the crash because four French citizens were aboard the flight.
Though Malaysian officials appeared eager to reach conclusions swiftly and put the mystery of Flight 370 behind them, Tony Abbott, the Australian prime minister, said Thursday that the ocean search would continue. “We owe it to the hundreds of millions of people who use our skies,” he said.
Meanwhile, Jean-Paul Virapoullé, the mayor of St.-André, Réunion, near where the wing debris was found, said Thursday that his town would organize a “meticulous search” of the beaches there next week.
“If it can soothe the terrible pain of these hundreds of families, the city of St.-André, with the agreement of the relevant international authorities, is ready to erect a memorial for the people who are missing,” the mayor said in the statement.
The person close to the investigation said that volunteers on Réunion turned in some additional debris to French aviation officials on the island on Thursday, but that a preliminary evaluation indicated that none of the objects were from a plane.
Still, David Griffin, an Australian scientist who has mapped ocean currents in the area, said Thursday that he believed more debris from Flight 370 could wash up on Madagascar, the much larger island nation to the west of Réunion.
“There could be a very large amount of debris floating, or a very small amount,” said Mr. Griffin, who is with the Commonwealth Scientific and Industrial Research Organization in Australia. “I am slightly surprised that something turned up at Réunion, rather than Madagascar, because Madagascar is so much bigger.”
Wen Wancheng, 63, whose son was on the aircraft, said finding one wing part did not resolve the mystery of Flight 370.
“The sort of closure the families want is to know what exactly happened to the plane, and have the bodies returned,” he said by telephone from Jinan, in eastern China.
That sentiment was shared by other relatives of Flight 370 victims around the world, some of whom said that the discovery of the wing part, known as a flaperon, only intensified the mystery.
“Ultimately in the end for the families to have a sort of closure, we need to know why it ended up in the ocean, what happened,” Sara Weeks, whose brother Paul was a passenger, said in an interview with Australian radio from Christchurch, New Zealand. “It is really important for everyone because if that plane can go missing, another one can.”
For some, the longing for more evidence has only grown stronger.
“It’s a piece of flaperon; it’s not my husband,” said Jacquita Gonzales, the wife of a Flight 370 crew member, Patrick Gomes. Ms. Gonzales was one of a small group of family members who spoke to reporters on Thursday in the Malaysian city of Petaling Jaya.
“Although they found something, it’s not the end,” she added. “They still need to find the whole plane and our spouses as well. We still want them back.”