Thirty former guards at the Auschwitz death camp could face charges of being an accessory to murder, according to the German prosecutor's office that investigates Nazi war crimes.
Kurt Schrimm, the head of the special office, said an investigation of 49 alleged former guards had yielded enough evidence to charge 30 of them still living in Germany. The oldest is 97.
A further seven suspects who live outside the country are still being investigated. Nine suspects have died since the investigation began in April, two could not be located and one was already under investigation in Stuttgart.
"The biggest enemy is time," Schrimm said. He warned the health of the suspects - and of possible witnesses - would make bringing them to trial difficult.
The announcement opens the way for a new wave of war crimes trials nearly 70 years after the end of World War II. Germany's Central Office for the Investigation of National Socialist Crimes, based in Ludwigsburg, has no powers to charge suspects but must send files to regional prosecutors.
These officials decide whether to press charges.
For more than 60 years, German courts prosecuted Nazi war criminals only if evidence showed they had personally committed atrocities, but since a 2011 landmark case all former camp guards can be tried. In that year a Munich court sentenced John Demjanjuk to five years in prison for complicity in the extermination of more than 28,000 Jews at the Sobibor camp, where he had served as a guard.