Right-wing British historian David Irving, who once famously said that Adolf Hitler knew nothing about the systematic slaughter of six million Jews, has been arrested in Austria on a warrant accusing him of denying the Holocaust. Irving, 67, was detained November 11 in the southern province of Styria on a warrant issued in 1989 under Austrian laws that make Holocaust denial a crime, police Maj. Rudolf Gollia, a spokesman for the Interior Ministry, said Thursday. Irving in the past has faced allegations of spreading anti-Semitic and racist ideas. He is the author of nearly 30 books, including "Hitler's War," which challenges the extent of the Holocaust. Besides his assertion that Hitler knew nothing about the Holocaust, he also has been quoted as saying there was "not one shred of evidence" that the Nazis carried out their "Final Solution" on such a scale. Irving remained in custody Thursday at a prison in Graz, 200 kilometers (120 miles) south of Vienna, the Austria Press Agency reported, although that could not be confirmed. If formally charged, tried and convicted, he could face up to 20 years in prison, said Otto Schneider of the public prosecutor's office.