Authorities said Friday they were investigating the discovery of dozens of skeletons, many of them babies or children with signs of physical handicaps, in what appeared to be a Nazi-era mass grave of euthanasia victims.

Following a tip from a resident, authorities in Arnsberg this week began searching the western town's Roman Catholic cemetery. So far, the remains of 51 people have been discovered, said prosecutor Ulrich Maass.

Many of the skeletons, which appeared to be of children ranging from newborns to 7-year-olds, had signs of physical handicaps, Arnsberg authorities said, adding that medical instruments have also been found in the grave.

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Maass, a prosecutor at the Dortmund-based Central Office for Investigation of Nazi-era Crimes, told The Associated Press he had begun a criminal investigation for at least 22 counts of murder in connection with the deaths, which appear to have been the result of Nazi-era euthanasia programs, but it was unclear if charges could be pressed.

"Of course, there is the question of how we are to prove these crimes after all this time. If the children were poisoned, that will be practically impossible," he said.

Maass expressed hope that several witness, including an elderly woman who worked during the war in the nearby Wickede-Wimbern Hospital where he suspects the children were killed, would be able to help his case.

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"A hospital administrator and a doctor are also still alive," Maass said.

Around 275,000 people, many of them children, who were deemed unfit were killed by doctors under the Nazis as part of a vast Europe-wide euthanasia program, according to the U.S. Holocaust Museum and other sources.