Skeletons of 22 children and 29 adults have been found in a suspected Nazi-era mass grave excavated in Germany.
The remains were exhumed from the cemetery of a Catholic church in the village of Menden-Barge.
Officials said the dead may have been victims of Adolf Hitler's "euthanasia" programme, under which many disabled people were murdered.
Hitler's Nazi regime killed more than six million Jews and other minorities across Europe during World War II.
"We assume that these were victims of the Nazi regime," state prosecutor Ulrich Maass said.
Mr Maass said authorities would search for evidence about the suspected killings and witnesses to any atrocities.
At least one witness, a former church assistant, said he saw corpses brought to the grave by horse-drawn cart.
But he admitted that it could be difficult to find enough strong evidence to bring charges against any individual, 61 years after the end of the war.
Poisons often used to kill victims would be hard to detect after so many years.
The prosecutor said a culture of secrecy surrounded the grave until recent years.
The cemetery is near the site of a hospital once run by Hitler's personal doctor Karl Brandt, who headed the "euthanasia" programme, called Action T4. Victims were killed by lethal injection or by carbon monoxide fumes piped into sheds from car exhausts.