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.
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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.