Terrorism fears quickly emerged on social media in the wake of the devastating Germanwings Flight 9525 plane crash that rattled Europe Tuesday. French officials said the plane, which rescue crews located high in the French Alps, had almost completely disintegrated in the crash, cementing earlier reports that there were likely no survivors.

While U.S. security officials said there was no evidence of terrorist activity, French Prime Minister Manuel Valls said “no explanation for the crash can be excluded.” The comments were made during an address before parliament Tuesday afternoon as search and rescue teams began scouring the wreckage by air and on foot.

"There is no indication of a nexus to terrorism at this time,” Bernadette Meehan, spokeswoman for the U.S. National Security Council, said in a statement, according to the Associated Press. The White House said U.S. officials were in contact with authorities in France, Germany and Spain regarding the plane crash that presumably left all 150 people dead. Most of the passengers were of German, Spanish and Turkish nationalities.

“We extend our deepest condolences to the families and loved ones of the 150 people on board,” a spokesman for the U.S. State Department said in an emailed statement. “We are reviewing whether any U.S. citizens were aboard the flight. The United States stands ready to offer assistance and support to the governments of France, Germany and Spain as they investigate this tragedy.”

Search crews located the crash site Tuesday in an area of the Alps that is inaccessible from the ground. Helicopters circled the area, and at least one was able to land close to the plane. Debris from the downed aircraft was spread out over a 100- to 200-meter (110- to 220-yard) area, the largest pieces of which are about the size of a small car, according to the AP.

French officials said the scene of the wreckage was one of total devastation. "Appalling scenes in these mountains,” Gilbert Sauvan, president of the general council of the Alpes-de-Haute-Provence, told Les Echos newspaper, according to the New York Times. “There is nothing left but debris and bodies.”

Germanwings Flight 9525, an Airbus A320, crashed in the French Alps in southern France on its way from Barcelona, Spain, to Düsseldorf, Germany, on Tuesday. Authorities said the plane had been flying at an “abnormal” altitude before it fell, and that it had descended rapidly from its cruising altitude of 38,000 feet to about 5,000 feet. The plunge lasted about eight minutes before the aircraft collided with the mountainside.