It was found on Tuesday by workers building a hydroelectric plant near the town of Lambach, close to the site of Gunskirchen, a satellite of the Mauthausen concentration camp. It contains the skeletons of 10 men aged between 19 and 22. The Nazi-hunter Simon Wiesenthal said they were probably Hungarian Jews on one of the death marches between concentration camps in the last few weeks of the war.
All building work on the site was halted yesterday as officials and Jewish experts tried to establish who the dead were and whether there were any more remains. If it is confirmed the victims were Jewish, the power-plant project could be in jeopardy as, according to Jewish rite, bodies should not be disinterred or reburied.
"A Jewish cemetery is a cemetery for eternity," said Paul Grosz, president of Austria's small Jewish community. "The peace of the dead cannot simply be forgotten and subordinated to existing or perceived necessities." The company building the plant promised to treat the dead with "adequate piety" but said it saw no reason to abandon the project.
The proposed plant has been the source of controversy for years, with ecological groups saying it was unnecessary and a threat to wildlife and woodland.
When work began in early January, protesters set up camp on the site, attracting widespread media coverage and winning supporters across the political spectrum. Parliament decided to debate the subject this week, finally meeting to do so on the day that the skeletons were found.
"We would not want there to be any linkage between the discovery of the grave and the ecological arguments but it has certainly added a new dimension to the subject," said Brigit Weinzinger, of the Global 2000 environmental group. "We feel the project should be halted in any event. But like most people we feel shocked and saddened by what has happened."
According to Mr Wiesenthal there were more than 100 mass graves in Austria, some containing more than 1,000 bodies. Many were unearthed in the years immediately after the war. But some, like that believed to have been found at Lambach, never came to light as Austrians collectively sought to suppress the memory of their participation in the Nazi regime.
"Many Austrians after the war did not want to talk about such things or admit that they knew about them," said Mr Grosz. "They preferred not to say anything. That is why, 50 years later, we are still coming across such things."