Berlin ? The skeletal remains of at least 51 people – many of them children – have been unearthed, and authorities suspect some were killed by the Nazis because they were disabled and considered worthless by the regime.

Prosecutors, acting on a tip from an aging witness, have opened a murder investigation despite the difficulty of finding conclusive evidence more than 60 years after the end of World War II and the likelihood that those responsible are dead.

“As long as we have even the slightest indication that the children were victims of the Nazi euthanasia program, we will keep on investigating,” prosecutor Ulrich Maass said Friday.