Authorities are investigating the dissemination over the Hanukkah holiday of anti-Semitic pamphlets in Pittsburgh's Squirrel Hill neighborhood, where a gunman killed 11 people while they prayed at a synagogue in October.
Pamphlets were also found in other Pittsburgh neighborhoods.
On Sunday, a spokesman said police and the city department of public safety were "taking this matter very seriously and will follow every investigative avenue."
Police said "such hate-filled material" will not be tolerated in the city by residents, city officials or law enforcement.
Robert Bowers, 46, has been charged with bursting into the synagogue and opening fire with a semi-automatic rifle and three pistols in the midst of Shabbat prayer services as he shouted: "All Jews must die."
Bowers faces an indictment that includes 44 counts of murder, attempted murder, hate crimes, obstructing free exercise of religion resulting in death, and other offenses that could yield the death penalty.
He has pleaded not guilty to the charges.
The shooting was the deadliest attack on Jews in U.S. history.
