A suspected Nazi war criminal accused of aiding in the killings of 216,000 Jews at a death camp and now awaiting an extradition hearing has been hospitalized.

A court order issued Monday noted that Johann Breyer, 89, had been hospitalized but did not cite his condition.

Breyer’s attorneys have said that he is in frail health.

Breyer, a retired toolmaker, has been in federal custody since his arrest last month at his longtime home in Philadelphia.

German authorities have said they hope to try him on accessory-to-murder charges for his guard service at the Auschwitz death camp in 1944. He has denied taking part in the mass killing of Jews and others there.

U.S. Magistrate Judge Timothy Rice canceled an extradition hearing scheduled for Thursday, citing Breyer’s hospitalization.

German authorities in the Bavarian town of Weiden issued a warrant for Breyer’s arrest in June 2013. The warrant accuses Breyer of 158 counts of accessory to murder, one count for each trainload of victims taken to the Auschwitz death camp in occupied Poland from May to October 1944. Breyer said in 2012 that he was assigned to a part of the camp that was not involved in the slaughter of Jews and others.