SEYNE-LES-ALPES, France -- Crews began a second day of searching on an Alpine mountainside where a German jetliner crashed without making a distress call Tuesday, apparently killing all 150 people on board.
Helicopters resumed flights Wednesday over the field of widely scattered debris, as a U.S. official confirmed that two Americans were among those on board Germanwings Flight 9525.
Crews were making their way slowly to the remote crash site through fresh snow and rain, threading their way to the rocky ravine. But CBS News correspondent Mark Phillips says the weather Wednesday was better than expected, bringing hopes that recovery efforts could speed along.
French Interior Ministry spokesman Paul-Henry Brandet said the overnight precipitation made the rocky ravine slippery, increasing the difficulty of reaching the steep area.
Phillips said retrieval of the victims would be the first priority for search crews, and it wasn't going to be easy. The plane came down in the most inhospitable, inaccessible terrain imaginable.
"Of course there are bodies," said Frédéric Petitjean, chief doctor at the local fire department, but he added that "identifying them will be hard... You see the state of the plane, so I'll let you imagine the state of the bodies."
On Tuesday, the cockpit voice recorder was retrieved from the site. French accident investigation agency BEA confirmed Wednesday morning that it had received the voice recorder at its headquarters and believed it could extract useful data from the device.
Key to the investigation is what happened in the minutes after 10:30 a.m. local time on Tuewsday, said Segolene Royal, France's energy minister. From then, controllers were unable to make contact with the plane.
The two "black boxes" -- actually orange boxes designed to survive extreme heat and pressure -- should provide investigators with a second-by-second timeline of the plane's flight.
The voice recorder takes audio feeds from four microphones within the cockpit and records all the conversations between the pilots, air traffic controllers as well as any noises heard in the cockpit.
The flight data recorder, which Cazeneuve said had not been retrieved yet, captures 25 hours' worth of information on the position and condition of almost every major part in a plane.
Royal and Cazeneuve both emphasized that terrorism was considered unlikely.
In Washington, the White House said American officials were in contact with their French, Spanish and German counterparts. "There is no indication of a nexus to terrorism at this time," said U.S. National Security Council spokeswoman Bernadette Meehan.
Germanwings Flight 9525, from Barcelona, Spain to Duesseldorf, Germany, went into an unexplained eight-minute steep descent that culminated with the crash, but even as it descended, it maintained a relatively normal airspeed, adding to the mystery about what could have happened.
The Airbus A320 was less than an hour from its scheduled landing when it began the descent. France's aviation authority said the pilots did not send out a distress call and had lost radio contact with their control center.
The plane left Barcelona Airport at 10:01 a.m. and had reached its cruising height of 38,000 feet when it suddenly went into the unexplained descent to just over 6,000 feet, Germanwings CEO Thomas Winkelmann told reporters in Cologne.
"We cannot say at the moment why our colleague went into the descent, and so quickly, and without previously consulting air traffic control," said Germanwings' director of flight operations, Stefan-Kenan Scheib.
The plane crashed at an altitude of about 6,550 feet at Meolans-Revels, near the popular ski resort of Pra Loup. The site is 430 miles south-southeast of Paris.
Germanwings is a budget subsidiary of Lufthansa, Germany's biggest airline. The parent company is, for now, calling the crash an accident.
Meanwhile, flowers were piling up in front of a Germany high school where 16 of the passengers were 10th grade exchange students. Students gathered for a service, crying and hugging one another over the loss of their classmates.
The majority of victims were European. Germany and Spain are believed to have lost the most lives in the crash. Britain's government confirmed Wednesday that three nationals were among those on board. Two of the passengers were Australian. The Japanese government says two of its citizens were on board as well. Two babies and two opera singers were on the plane.
While investigators searched through debris on steep and desolate slopes, families reeled with shock and grief. Sobbing relatives at both airports were led away by airport workers and crisis counselors.
"The site is a picture of horror. The grief of the families and friends is immeasurable," German Foreign Minister Frank-Walter Steinmeier said after being flown over the crash scene. "We must now stand together. We are united in our great grief."
It took investigators hours to reach the site Tuesday, led by mountain guides to the ravine in the southern French Alps, not far from the Italian border and the French Riviera.
Video shot from a helicopter and aired by BFM TV showed rescuers walking in the crevices of a rocky mountainside scattered with plane parts. Photos of the crash site showed white flecks of debris across a mountain and larger airplane body sections with windows. A helicopter crew that landed briefly in the area saw no signs of life, French officials said.
"Everything is pulverized. The largest pieces of debris are the size of a small car. No one can access the site from the ground," Gilbert Sauvan, president of the general council, Alpes-de-Haute-Provence, told The Associated Press.
"This is pretty much the worst thing you can imagine," said Bodo Klimpel, mayor of the German town of Haltern, filled with grief after losing the 16 students and their two teachers.
Merkel, French President Francois Hollande and Spanish Prime Minister Mariano Rajoy were to visit the site Wednesday.
Germanwings serves mostly European destinations. Tuesday's crash was its first involving passenger deaths since it began operating in 2002. The Germanwings logo, normally maroon and yellow, was blacked out on its Twitter feed.
Lufthansa CEO Carsten Spohr called it the "blackest day of our company's 60-year history." He insisted, however, that flying "remains after this terrible day the safest mode of transport."
Contralto Maria Radner was returning to Germany with her husband and baby after performing in Wagner's opera "Siegfried," according to Barcelona's Gran Teatre del Liceu. Bass baritone Oleg Bryjak had appeared in the same opera, according to the opera house in Duesseldorf.
Authorities faced a long and difficult search-and-recovery operation because of the area's remoteness.
Brandet, the French Interior Ministry spokesman, said the crash site covered several acres, with thousands of pieces of debris, "which leads us to think the impact must have been extremely violent at very high speed."
Winkelmann said the pilot, whom he did not name, had more than 10 years' experience working for Germanwings and Lufthansa.
The aircraft was delivered to Lufthansa in 1991, had approximately 58,300 flight hours in some 46,700 flights, Airbus said. The plane underwent a routine check in Duesseldorf on Monday, and its last regular full check took place in the summer of 2013.
The A320 plane is a workhorse of modern aviation, with a good safety record.
The last time a passenger jet crashed in France was the 2000 Concorde accident, which left 113 dead.