The authorities say the group’s crimes went far beyond that attack. The men are suspected of committing at least 14 bank robberies, including one in Eisenach the day they died. The group is also suspected of detonating a bomb outside a hairdresser’s shop in an immigrant neighborhood of Cologne in 2004, wounding 22 people. The propaganda video includes a photograph of a bomb packed with nails, similar to the one used in Cologne.

Image Credit... The New York Times

Investigators said Sunday that they were looking at other crimes that might be the work of the group, including a bombing in Saarbrücken in March 1999 during an exhibition about the German military during World War II, and another at a Jewish cemetery in Berlin in March 2002. The police are also looking into whether the group may have been behind the killing earlier this month of a man in Döbeln who was selling kebabs.

The authorities were scrambling to determine whether the known members of the group had connections to other undiscovered criminals, as officials from across the political spectrum demanded to know how the group could have operated undetected for so long.

“This is a devastating failure,” said Hajo Funke, an expert on rightist extremism at the Free University in Berlin. “There is still a lack of public will to go after National Socialistic groupings in a sufficient manner.”

The federal prosecutor’s office announced that the police had arrested one suspect in the group near Hanover on Sunday. Prosecutors identified the man only as Holger G., and said that he had been in contact with Mr. Mundlos and Mr. Böhnhardt, the two central suspects, since the late 1990s. They said he lent his passport to the group and rented camper vans for them several times, including one used in the shootings of the police officers in Heilbronn.

Violent far-right extremism came under renewed scrutiny throughout Europe after the mass murder in Norway in July by a man with connections to extremist groups. The German government has worked to contain even the slightest resurgence of such extremism, but far-right political groups like the National Democratic Party continue to find some support, especially in the states of the former East Germany. Extremists operate in loose networks, especially in Saxony, Saxony-Anhalt and Thuringia, Mr. Funke said.