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BERLIN — German prosecutors say they have been notified that a former guard dubbed the "accountant of Auschwitz" has died.

Hannover prosecutor Kathrin Soefker says a lawyer informed her office that Oskar Groening died Friday in a hospital. Soefker says the office is awaiting an official death certificate.

Defendant Oskar Groening awaits the proclamation of his verdict at the court house on July 15, 2015 in Luenenburg, Germany. Tobias Schwarz / Pool via EPA

The lawyer, Hans Holtermann, didn't immediately respond to a request for confirmation. The 96-year-old Groening's death first was reported Monday by German weekly Der Spiegel.

Groening was convicted in Lueneburg in 2015 as an accessory to the murder of 300,000 Jews. All of his appeals were rejected and he was due to begin a four-year prison term soon.

Related: Ex-Auschwitz guard, Oskar Groening, fit for prison

Groening testified at his trial that he oversaw the collection of prisoners' belongings and ensured valuables and cash were separated to be sent to Berlin. He said he witnessed individual atrocities, but did not acknowledge participating in any crimes.