The former SS soldier and Nazi war crimes suspect Adolf Storms has died before he could be brought to trial.
Storms, who was 90 years old, was on the Simon Wiesenthal Center's list of most-wanted Nazi suspects.
He was accused of the massacre of at least 57 Jewish forced labourers in Austria at the end of World War II.
Prosecutors in Germany were investigating the accusations against him and preparing a trial.
The prosecutor in the city of Dortmund, Andreas Brendel, said investigators had recently been checking if Storms was fit for trial.
Mr Brendel said he had had strong evidence against Storms.
The former SS officer and unidentified accomplices allegedly forced the labourers to hand over their valuables and kneel by a grave before shooting them.
Storms was also accused of having shot another man on the day after the massacre.
He was alleged to have shot the man because he was too weak to take part in a forced march.
Several former members of the Hitler Youth, who had helped the SS guards during the march, gave witness statements against Storms.
The accused worked as a railway station manager for decades until a student at the University of Vienna found his name in documents alleging his involvement in war crimes.
The student and his professor then tracked down Storms, who said he did not remember the killings.