In Mr. Lubitz’s hometown, Montabaur, people who knew him or his parents said the co-pilot’s girlfriend had swiftly gone with her family to a hotel to escape the news media. The girlfriend was questioned by investigators.

The mood Friday in Montabaur contrasted drastically with the outpourings of grief in other communities that lost residents in the crash. Signs of mourning were restrained, perhaps reflecting shame at what a native son appeared to have done.

At a Roman Catholic church at the edge of Montabaur’s old quarter, a few candles had been placed near the front door with a small hand-lettered sign expressing sympathy for the victims’ families. At Mons Tabor Gymnasium, a local high school from which Mr. Lubitz graduated in 2007, a German flag flew at half-staff, but otherwise, there was no reminder of the loss of life.

At a Protestant church on the edge of town, one of two affiliated churches where Mr. Lubitz’s mother plays organ, the shades of the minister’s office were drawn and no one answered the doorbell.

On Thursday, the French prosecutor leading the investigation said the evidence from the cockpit voice recorder suggested that Mr. Lubitz, a former flight attendant with a passion for flying, had locked the pilot out of the cockpit and deliberately set the plane on a descent into the Alps.

Image Andreas Lubitz, the co-pilot of the Germanwings jetliner that crashed in the French Alps on Tuesday, ran a half marathon in Hamburg, Germany, in 2009. Credit... Foto Team Mueller, via Reuters

The crash claimed victims from more than a dozen countries, including Germany, Spain and the United States.

Police officers and rescue workers on Friday continued to search the site of the crash for victims’ remains, along with other clues and DNA that could help them identify the dead. Families continued to trickle into Seynes-les-Alpes, France, a village near the crash site, with 20 more people arriving mostly from Germany and Colombia, said Francis Hermitte, the village’s mayor.

There are now two investigations into the crash, in France and in Germany. Spanish investigators are also at the crash site, along with French teams, said Capt. Benoit Zeisser, the head of a local police operations center.

In an interview with the French broadcaster i-Télé, Prime Minister Manuel Valls of France said it was incumbent upon Lufthansa to reveal as much information as possible to help “understand why this pilot got to the point of this horrific action.”

President Joachim Gauck of Germany attended a memorial service in Haltern am See on Friday for the 16 high school students and two teachers who died in the crash, German news reports said. He was accompanied by the state premier of North Rhine-Westphalia, Hannelore Kraft. He was also to meet with friends and families of the victims.