According to the Times, the voice recorder would have captured up to two hours of the pilots' conversations, as well as any other noises in the cockpit, including alarms. Investigators hope to find some clue as to what caused the crash.
Although the plane descended rapidly for eight minutes before crashing, no mayday or distress signals were sent, the Guardian reports. There were 10 minutes of radio silence before the plane crashed into a ravine at around 430 mph.
"It's a sharp ridge and steep slope that is difficult to access. We have seen the catastrophe and terrible things. It was clear the victims were there in the midst of the destroyed aircraft," French MP Christophe Castaner, told journalists. "We saw women, men, children, and babies. Yes, we saw babies."
Castaner was one of the first on the scene, flying over the crash site twice. "Our hope was to find people who could be saved," he said. "It disappeared when we saw the state of the plane."
The search for bodies and the second black box was called off for the night, a spokesman for the French interior ministry in Seyne-les-Alpes, Pierre-Henri Brandet, said.