Germanwings Flight 4U 9525 was traveling to Dusseldorf, Germany, from Barcelona, Spain. It crashed near Barcelonnette, a town in the Alpes de Haute-Provence region.
It is not yet known why the accident, which occurred at 11:20 a.m. local time (6:20 a.m. ET), took place. France's interior minister, Bernard Cazeneuve, said that one of the plane's black boxes had been found.
"We saw an aircraft that had literally been ripped apart, the bodies are in a state of destruction, there is not one intact piece of wing or fuselage,'' Brice Robin, prosecutor for the city of Marseille, told Reuters after flying over the crash site in a helicopter.
French officials suspended their search of the area as night fell on Tuesday.
A representative for Germanwings said at its press conference that the plane fell into a steep descent, which lasted for eight minutes, Reuters reported. The budget airline is owned by Lufthansa, which took delivery of the plane in question in 1991. This crash is the first since the subsidiary was launched in 2002.
The airline said it would seek to find out "as quickly as possible" why the plane had crashed.
"For the time being, we say it's an accident. There's nothing more that we can say right now. Everything else would be speculation," Heike Birlenbach, vice president of Europe sales and services for Lufthansa, said.
At a press conference, a representative for the budget German airline said there were 144 passengers, including two babies and a school party of 16 children, and six crew members on board.
Sixty-seven of the passengers are believed to be German, the company said, although it stressed that number could change. Spain's deputy prime minister said that 45 passengers had Spanish names, Reuters reported.
U.S. President Barack Obama said in a press conference that officials were working to confirm whether Americans were on the plane.
Representatives from Germanwings, Lufthansa and Airbus went to the crash site. German Chancellor Angela Merkel said she would travel there on Wednesday.
French police Capt. Benoit Zeisser told CNBC that official helicopters had located the crash site, which is not easily accessible. Officials have said that terrain and snow have made searching the area difficult.
If the black box's data is intact, it can offer details into what happened immediately before the crash, said Deborah Hersman, former chair of the U.S. National Transportation Safety Board and CEO of the National Safety Council, on CNBC's "Power Lunch."
"You're going to get sense of not just what the aircraft was doing and how that descent was being managed, but you'll get a sense of what the conversations going on in the cockpit were like," she said.
The weather conditions were not bad at the time of the crash, according to Zeisser.
The flight path and descent "strongly suggest" that the pilots were incapacitated as the plane lost altitude, Anthony Roman, a former pilot and president of Roman and Associates, told CNBC's "Closing Bell" on Tuesday.
Aviation expert Michael Boyd, chairman of The Boyd Group consultancy, told CNBC there were no known issues with Germanwings.
"Anything involved with Lufthansa is going to be clean as a whistle as far as maintenance and operations goes," he said on CNBC's "Squawk Box."
"There hasn't been anything untoward with the A320 series. ... It's a very reliable airplane."
The A320 is a commonly used twin-engine, single-aisle aircraft that seats 150 passengers.
The plane that crashed had flown around 58,300 flight hours across 46,700 flights, according to Airbus. It had been inspected on Monday.
—CNBC's Katy Barnato contributed to this report.