This is a developing story.

A Germanwings Airbus A320 carrying 144 passengers and six crew members crashed in southern France on Tuesday. The aircraft, with the call sign 4U9525, was traveling from Barcelona to Dusseldorf.

French Transport Minister Alain Vidalies reportedly said that the plane sent out a distress signal at an altitude of 5,000 feet, "in an abnormal situation," adding that the crash took place shortly after the distress call. French Interior Ministry spokesman Pierre-Henry Brandet said that debris from the plane crash had been located, and that the crash site's remoteness could trigger "an extremely long and extremely difficult" search and rescue operation. 

According to Flightradar24, an aircraft-tracking site, the plane went off radar near Digne in southern France. Search and rescue teams are headed to the crash site at Meolans-Revels, Eric Ciotti, head of the regional council, said, according to the Associated Press (AP).

"We do not yet know what has happened to flight 4U 9525. My deepest sympathy goes to the families and friends of our passengers and crew on 4U 9525. If our fears are confirmed, this is a dark day for Lufthansa. We hope to find survivors," Carsten Spohr, Lufthansa's chief, said. Germanwings is a Cologne, Germany-based low-cost carrier owned by Lufthansa.

Meanwhile, the French transport ministry said that German air safety experts are on the way to the crash site, according to Reuters.

French president Francois Hollande said that there are likely "no survivors" from the plane, which crashed between Digne et Barcelonnette in southern France, AP reported. "Conditions of the accident are not yet clear but lead us to believe there will be no survivors," Hollande reportedly said, adding that the crash site was a remote area.

France's transport minister reportedly said that the plane had sent a distress signal. According to Flightradar24, the plane initially climbed to 38,000 feet before it began descending at a rate of about 3,000 feet to 4,000 feet per minute, following which it lost radar contact at an altitude of 6,800 feet.

French Prime Minister Manuel Valls reportedly said that most of the passengers on board Flight 4U9525 were German nationals.