French air investigators are examining a black box cockpit voice recorder (CVR) from a Germanwings Airbus A320 to try to solve the mystery of why the aircraft crashed into a mountain in the southern Alps on Tuesday, killing all 150 people on board.

Victorian mother Carol Friday and her son Greig were on the ill-fated German jetliner en route from Barcelona, Spain, to Dusseldorf, Germany, as well as two infants and 16 school children.

Interior Minister Bernard Cazeneuve told French radio station RTL on Wednesday the black box that had been recovered from the crash site was damaged and would need to be repaired “in the coming hours”.

• How the Germanwings tragedy is unfolding
• Australian plane crash victims named
• Australians killed in plane crash
• Flight change saves footballers

“The enquiry must begin today,” Mr Cazeneuve said.

Transport Minister Alain Vidalies said that if voices have been recorded, the investigation would proceed “fairly quickly”.

“After that, if we have to analyse the sounds, that’s a job that will take several weeks, but it’s a job that can offer us some explanations,” Vidalies told French radio.

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.

Mr Cazeneuve reportedly ruled out a terrorist attack as the cause of the Germanwings air crash.

“The debris from the plane is spread over one-and-a-half hectares, which is a significant area because the shock was significant,” he said.

“But it shows that the plane did not appear to have exploded.

“The theory of a terrorist attack is not the theory we’re focusing on.”

Nevertheless, the minister added cautiously that “all theories must be carefully examined until we have the results of the enquiry”.

No distress call was made from the Germanwings plane before the crash, French authorities said.

The flight was heading north after climbing from Barcelona across the Mediterranean. It swung left to fly inland en route to Dusseldorf and soon after made its sharp, final descent.

The aircraft made an eight-minute descent after reaching cruising altitude to crash into the French Alps about 100 kilometres north of Nice.

Investigators are puzzled as to why the crew did not send out a mayday or distress signal as flight U49525 rapidly lost altitude for eight minutes, or why the pilot did not change course to avoid smashing into a rocky ravine at around 430mph (700kmh).

In the last 10 minutes of the flight there was total radio silence from the crew of the Barcelona–Dusseldorf flight operated by Lufthansa’s low-cost subsidiary.

The recovery operation resumed on Wednesday, however heavy fog and snow surrounding the crash site may hinder the process.

The inaccessibility of the crash site could also hamper efforts, with helicopters finding it near impossible to land in the rocky and perilously steep mountain terrain.

“It’s a zone that is very difficult to access, very slippery. There was rain and snow overnight. So we need to secure the zone before the investigators begin their work,” a spokesman for the French interior ministry, Pierre-Henry Brandet, told reporters.

“We are not in a race against time,” he said.

“We need to move forward methodically.”

Germanwings has reportedly retired the flight number 4U9525 and assigned a new flight number to the Spain to Germany route.

The airline’s managing director, Thomas Winkelmann, said routine maintenance of the aircraft had been carried out the day before by Lufthansa technicians in Dusseldorf, and said the company would work closely with investigators.

Mr Wikelmamnn said that the plane’s captain had more than 10 years’ flight experience with Lufthansa and Germanwings, including 6,000 flight hours with this model airbus.

The aircraft was 24 years old and was bought by Lufthansa in 1991.

It had received a major inspection in the summer of 2013.

Foreign Minister Julie Bishop said in a statement on Wednesday morning that two Australian consular officials are on their way to the French town of Gap where they will liaise with French authorities and seek to identify any bodies.

“We are coordinating with the French authorities,” she said.

“Our thoughts are with the families.”

Civil aviation investigators from France’s Bureau d’Enquetes et d’Analyses are expected to hold a news conference on Wednesday afternoon.

Investigators face daunting search for clues to Germanwings flight disaster http://t.co/naRkAYwF91 pic.twitter.com/ACySsVETdd”

— Mr. C (@dorrian60) March 25, 2015

“Vi que a esa altura el avión no iba a atravesar la montaña”: testigo de accidente aéreo http://t.co/7nKnqS37sE pic.twitter.com/IgzJdwFnve — Milenio.com (@Milenio) March 25, 2015

daybreak at Seyne les Alpes where recovery ops for #GermanWings jet resume for second day. pic.twitter.com/IXo4FdpIxg

— Greg Keller (@Greg_Keller) March 25, 2015

‘Schwarzer Tag’ … A Dark Day. #Germanwings victims remembered. pic.twitter.com/aiufO3N1CK

— Stuart Greer (@globalgreer) March 25, 2015

– with AAP