Malaysia was intensely criticized early in the Flight 370 mystery for failing to quickly disclose that its military radar had picked up an unidentified aircraft the night the Boeing 777 disappeared. Now its reticence has given way to what looks like haste — compared to other countries involved, at least — and that has left relatives of the missing as exasperated as ever.

Prime Minister Najib Razak called a press conference at 1 a.m. Thursday in Kuala Lumpur to say that a wing fragment found on an Indian Ocean island had been definitively linked to Malaysia Airlines Flight 370. That announcement came an hour ahead of one from French investigators that differed in a significant way: They confirmed the part was from a 777, but did not have proof that it was from Flight 370.

American and Australian officials echoed the French, leaving the Malaysians on their own, though no less convinced that they are in the right.

"It is our plane and we know it best. Since the French is the investigating team here, they do not want to take our word for it and they want to do more tests — that is fine with us," an official in Najib's office said Friday. "We are accustomed to criticism from day one, but please give us credit because we are doing our best to cope with this."

The official — who spoke on condition of anonymity because he was not authorized to discuss the difference of opinion — said the Malaysian government owes it to the public and the families of those on the plane to reveal what it knows and to deliver the news first.

Najib's early-morning news conference underlines the lengths Malaysia is willing to go to announce Flight 370 developments first, 17 months after the plane vanished with 239 people aboard on a flight from Kuala Lumpur, the capital, to Beijing. In the weeks immediately following the March 8, 2014, disappearance, it was often slow to release critical data.

But its latest effort to be transparent clearly backfired, generating confusion when French authorities delivered a different message. A barnacle-crusted object found last week on French-held Reunion Island is definitely a 777 part known as a flaperon, the French said, but they have yet to positively identify it as a piece of Flight 370.

Criticism of the handling of the Flight 370 investigation is not at all limited to Malaysia. Australia, which is overseeing the search for the plane because it is closest to the search area, trumpeted several leads that turned out to be false.

Ironically, the difference between the Malaysian and French views on the flaperon mean little to the search itself. Since no other 777 on Earth is missing, the part seems assured of being from Flight 370. No one involved in the investigation is suggesting an alternative possibility. The search for the plane, in a stretch of Indian Ocean far from Reunion, continues as it did before the wing part was found.

At the same time, the world — and especially relatives of the lost — have waited a long time for the moment when some bit of Flight 370 is revealed. The dueling announcements left many wondering whether that moment had truly come. Some questioned why the countries involved couldn't get on the same page before speaking publicly.

In Beijing, about 30 Chinese relatives of Flight 370 passengers marched Friday to the Malaysian Embassy hoping to talk to an official about why Malaysia confirmed the part came from the plane when French investigators had not. They scuffled briefly with police, who blocked the relatives from approaching the mission.

Ghislain Wattrelos, who lost his wife and two of his children when Flight 370 disappeared, said he was baffled by the comments by Malaysian authorities.

"We are delighted that the debris ended up in France," Wattrelos told BFM television in France on Thursday. "I have a lot more confidence in my country than in Malaysia and Australia, who have lied to us since the beginning."

Some criticism came from within Malaysia itself. Opposition lawmaker Liew Chin Tong said in a statement that Liow must explain "the haste and hurry" to declare the wreckage came from Flight 370.

"A quick conclusion will not do justice to the next of kin of the victims," he said.

Malaysian Transport Minister Liow Tiong Lai said later Thursday that the differences with other countries amounted to "a choice of words." But then Liow added to the confusion, saying a Malaysian team had found more debris on Reunion Island, including a window and some aluminum foil, and had sent the material to local authorities for French investigators to examine.

"I can only ascertain that it's plane debris," Liow said. "I cannot confirm that it's from MH370."

French officials involved with the investigation in both Paris and Reunion were baffled. None were aware of any discovery or material in French custody. The Paris prosecutor's office, which is spearheading a French legal inquiry into the crash, later denied there was any fresh debris, before French officials — notoriously cautious when it comes to air accident investigations — again retreated into silence.

A spokesman for Australian Transport Minister Warren Truss said in a statement Friday that while additional material has been handed to police in Reunion, none of it appears to have come from the plane.

Liow also sparked further questions when he said that a maintenance seal and the color tone of the paint on the wing part, known as a flaperon, matches the airline's records. On Friday, an Australian government official said the paint is not a unique identifier for Flight 370; rather, it comes from a batch that Boeing used on all its planes when the missing plane was manufactured. The official spoke on condition of anonymity because he was not authorized to comment publicly.

French government officials have not addressed the conflicting information coming from Malaysia. "I hope that all of this can be verified, but we have to take it to its end," French Defense Minister Jean-Yves Le Drian told RTL radio.

Authorities have jumped to incorrect conclusions several times in the Flight 370 saga.

Australia's credibility as search leader suffered a battering thanks to a series of false leads that were oversold by its government, which was eager to boast success after the hunt shifted to its search and rescue zone in the Indian Ocean.

Two apparent large objects spotted in satellite imagery off the west Australian coast in March 2014 were declared the "best lead" yet, before they turned out to be unrelated. The next month, Prime Minister Tony Abbott said officials were confident that a series of underwater signals search crews had detected were coming from the plane's coveted black box data recorders. That was also wrong.

The failure to find a single piece of Flight 370-related debris in a surface search covering 4.6 million square kilometers (1.8 million square miles) over six weeks raised serious questions about whether they were looking in the right place. And the search area has been altered many times.

Australian Transport Safety Bureau chief commissioner Martin Dolan denied his agency, which is leading the search, had misled anyone or withheld information.

"As soon as new or changed information comes to light, we make it available," Dolan told The Associated Press on Friday.

The ATSB has also faced criticism for making a mistake in its original drift modeling, which initially predicted debris would wash ashore in Indonesia, rather than the area east of Africa where the flaperon turned up. The bureau issued a statement this week saying a revised analysis showed that, in fact, debris could be carried by currents to the area near Reunion Island.

Dolan said the ATSB didn't withhold that error, and instead had been working with Australia's national science agency, CSIRO, to recalculate the drift area after noticing flaws in the model in November.

"We had to work with CSIRO to check the facts and as soon as we had something that was checked, we published it," Dolan said. "We were in the process with CSIRO of publishing that revised drift modeling when the flaperon turned up at Reunion."

Until the wing flap washed ashore last week, investigators had not found a single physical clue linked to the missing plane, despite a massive air and sea search. Officials believe it crashed in the southern Indian Ocean, killing everyone aboard, but are unsure of the cause.

The discovery of the wing flap refocused the world's attention on the investigation, which many hope will finally yield clues into the plane's fate. France said it is deploying a search plane, helicopters and boats around Reunion in hopes of spotting more debris that might be from the missing jet.

But information from the French, in particular, has been scant. The BEA, as the French agency that investigates air crashes is known, rarely comments publicly, instead eventually releasing the information via its detailed reports. In the case of Air France Flight 447, which crashed in the south Atlantic in June 2009, the final report was published in July 2012. The legal investigation was concluded only in July 2014, and the case still has not gone to trial.

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Gelineau reported from Sydney. AP writers Rod McGuirk in Canberra, Australia, Paul Joshua in Kuala Lumpur, and Thomas Adamson and Lori Hinnant in Paris contributed to this report.