Egyptian authorities have confirmed to EgyptAir that the wreckage of missing Flight MS804 has been found.
The plane was believed to have crashed en route from Paris to Cairo early Thursday with 66 people on board. Authorities said in a statement that the wreckage was found near Karpathos Island. The Egyptian investigation team will continue its search for other remains of the missing plane, according to EgyptAir's statement.
A senior U.S. Intelligence official familiar with U.S. capabilities in the region told NBC News that we do not know the cause, but "phenomenology" (infrared and multispectral images) indicate strongly there was an explosion on Egyptair MS804. The cause remains unclear, the source said. The U.S. has what is described as a "persistent stare" on the region, which collects everything from sound waves through multispectral images to pressure.
Earlier, Egypt's aviation minister told a news conference that there are no known security issues with passengers on the missing plane. Further checks were, however, underway. He added that the plane was more likely to have been brought down by a terror attack than a technical failure.
Two U.S. intelligence officials told NBC News there was "nothing finite, nothing specific" in chatter about a coming attack on aviation. There is nothing out there yet to confirm "foul play," according to the officials.
The Greek army deployed two aircraft, a frigate and two helicopters to the search and rescue operation 130 nautical miles south-southeast of the Greek island of Karpathos. The announcement was in addition to shipping data purportedly showing other marine traffic changing course to help the operation.
The U.S. State Department said that while it is still working on this case, it currently does not see any indications that American citizens were on EgyptAir MS804.
Reports of what could have happened to the plane in the moments before its disappearance started to emerge throughout the morning. Greek Defense Minister Panos Kammenos told a news conference that the plane had made "sudden swerves" and then plunged before dropping off radar.
Meanwhile, Egypt's civil aviation minister, Sharif Fathy, told a news conference that "no hypothesis had been ruled out" and that it could be a "terrorist act or a technical act." He refused to say the plane had "crashed," however, and said he would use the term "missing plane" until debris was found.
Greece has banned flights from an area stretching 40 miles around the last point of signal from the flight.
EgyptAir is updating its Twitter account regularly and said Egyptian Prime Minister Sherif Ismail had arrived at the airline's crisis center after cutting short a visit to Jeddah, Saudi Arabia.
The airline urged restraint from the media in the reporting of the incident amid conflicting accounts about distress signals from the missing plane.
News of the incident emerged in the early hours of Thursday. In an Arabic-language Facebook post just before 5 a.m. local time, EgyptAir cited an "official source" as saying the flight, which took off from Paris' Charles de Gaulle Airport at 11.09 p.m. Paris time, had "disappeared from radar in the early hours of (the) day."
In a series of subsequent tweets and statements, EgyptAir said the plane — an Airbus A320 — was carrying 56 passengers, including one child and two infants, as well as three of the airline's security personnel and seven crew members, taking the total number of people on board to 66.
It also said the plane disappeared 10 miles into Egyptian airspace — a distance confirmed by the country's Civil Aviation Authority, according to Reuters — and that the jet was manufactured in 2003. The "aircraft commander" had 6,275 hours of flight experience, including 2,101 on the same model plane, and the assistant pilot had 2,766 hours of experience, the airline said.
EgyptAir also released a list of the passengers' nationalities: 15 French, 30 Egyptians, two Iraqis and one person each from the U.K., Belgium, Kuwait, Saudi Arabia, Sudan, Chad, Portugal, Algeria and Canada.
French President Francois Hollande spoke to Egyptian President Abdel Fattah el-Sisi, according to a statement released by Hollande's office in the hours after the disappearance.
"They agreed to cooperate closely to establish as soon as possible the circumstances of the disappearance," the statement said. "The President of the Republic shares the anguish of the families affected by this tragedy."
Ellis Taylor, an Asia editor at Flightglobal magazine, noted the disappearance at 37,000 feet was unusual.
"Accidents are usually at landing or takeoff," he told CNBC. "Something from that height and so far into the flight indicates that something has gone quite seriously wrong on board."
He said the aircraft type had a good safety record. Airbus shares fell 1.2 percent when European markets opened Thursday, however, and other travel and leisure stocks declined.
Because the flight disappeared in Egyptian airspace, Taylor said he expected search and rescue operations to relatively quickly locate wreckage or an oil slick.
"It seems they have a good fix on where it was when it disappeared from radar. It should narrow down the search pretty easily," he said.
A Flightradar24 spokesman said that MS804 was on a normal course that was consistent with other flights bound for Cairo from Western Europe. Data from Flightradar24 indicated the plane's altitude didn't change significantly in the minutes leading up to its disappearance from radar.
In October a Russian holiday jet crashed in Egypt's Sinai region, killing all 224 people on board.
The Airbus A321, operated by Russian airline Kogalymavia under the brand name Metrojet, was flying from the Egyptian Red Sea resort of Sharm el-Sheikh when it went down in the central Sinai soon after daybreak, crashing into a mountainous area shortly after losing radar contact while near cruising altitude.
Russia said that the plane had been brought down by a bomb, as did the U.S. and other Western governments, and the Islamic State (IS) militant group claimed responsibility. But Egypt said that its investigations revealed no sign of terrorism.
Reuters reported in January that an EgyptAir mechanic, whose cousin had joined IS, was suspected of having planted a bomb on the flight.
And in March, an EgyptAir flight from Alexandria to Cairo was hijacked by a man who claimed to be wearing a suicide belt. He forced the plane to land in Cyprus, but authorities said later that the suicide belt was fake.
— NBC News' William Arkin contributed to this report.