EgyptAir Flight MS804 was flying from Paris to Cairo and vanished from radar with 66 people on board.
The Airbus A320 crashed into the Mediterranean Sea but the cause is unclear.
One child and two infants were among the 30 Egyptians, 15 French and 10 other nationalities on board.
EgyptAir retracted a previous statement that wreckage was found. Earlier, Greek officials denied that debris recovered was from the plane.
EgyptAir Flight 804 plummeted into the Mediterranean Sea early Thursday while en route from Paris to Cairo with 66 people on board, and authorities were investigating whether the plane was taken down by terrorists.
Search teams scoured the sea for possible wreckage on Thursday. EgyptAir said some of the plane's wreckage was found near the Greek island of Karpathos late Thursday, but later retracted the statement to CNN. Greek officials denied that any debris recovered so far was linked to the plane.
EgyptAir Flight MS804 left Paris at 11:09 p.m. and was scheduled to land at 3:05 a.m., Cairo time. It was cruising at 37,000 feet when it vanished from radar around 2:45 a.m. Cairo time.
The cause of the crash hadn't been determined. U.S. intelligence officials told NBC News that imagery suggests there was an explosion on the plane. However, U.S. officials cited by Reuters contradicted that claim, saying the imagery being reviewed showed no signs of an explosion so far.
"At this time we do not yet know definitively what caused the disappearance of Flight 804," the White House said in a statement Thursday night.
The search operation involved a frigate from Greece, as well as French, American, Greek, Turkish and Egyptian military planes.
Earlier, search teams spotted two objects in the sea 230 nautical miles south of the island of Crete, a Greek official told The Associated Press. An Egyptian ship captain posted images on Facebook that he claimed show a yellow lifejacket and part of a plane chair.
Officials know the pilot, Mohamed Saeed Shaqeer, 36, had more than 6,000 hours of flight experience, the airline said. The co-pilot, 24-year-old Mohamed Ahmed Mamdouh, had nearly 3,000 flying hours. No adverse weather was spotted at the time of the jet's disappearance.
"Our crew was entirely professional," EgyptAir's Adel told CNN. He added that the pilot was "incredibly professional, incredibly experienced."
Authorities have not ruled out terrorism as a potential cause of the crash. In a press conference, Hollande said he has no certain information about the disappearance.
“When we have the truth, we will draw our conclusions; whether this was an accident or something else, perhaps terrorist. We will have the truth,” Hollande said.
Egypt Civil Aviation Minister Sherif Fathi said at a press conference that a terror attack was a possibility, although he noted that he was not happy with "people making assumptions.”
U.S. presidential hopefuls began reacting to the news later Thursday. "It does appear that it was an act of terrorism -- exactly how, of course, the investigation will have to determine," Democratic presidential candidate Hillary Clinton told CNN.
The plane descended 22,000 feet and took two sharp turns, the Greek defense minister said, according to the French newspaper Le Figaro. Egypt received no distress signal from the plane, according to Fathi.
The pilot's abrupt turns and lack of distress call suggest a bomb is more likely to be the cause than structural or mechanical failure, former U.S. National Transportation Safety Board member John Goglia told AP. He cautioned that no potential cause could be ruled out at this stage.
In Paris, a crisis center was set up for families in the Hotel Mercure at Charles de Gaulle Airport. Another center for relatives will be set up in Paris later on Thursday, the French newspaper Le Parisien reported.
A man who sat crying in Cairo airport told a Reuters reporter: "How long will Egypt live if human lives are so cheap?”
Relatives of passengers seeking more information can call +20 2-2598-9320 from outside Egypt. The French Foreign Ministry has also released an emergency phone number: +33 1 43 17 55 95.
Other recent air disasters have triggered alarm within the security and aviation industries.
Last October, a Russian airliner carrying 224 passengers from the Egyptian resort town of Sharm el Sheikh crashed, killing all those aboard. The self-described Islamic State later took credit for the incident, claiming to have brought down the flight with an explosive.
In March, a man with a fake suicide belt hijacked an EgyptAir flight with 81 people flying from Alexandria, Egypt, to Cairo and forced it to land in Cyprus. No one was harmed. The man, who a Cyprus official said seemed unstable, was arrested. Authorities didn't classify the incident as terrorism.
Paris increased security at its Charles de Gaulle Airport following the November terror attacks in the city.
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