A fire official says the second floor of the federal court building in Philadelphia has been evacuated after authorities found a letter containing a threat about anthrax.

First responders outside federal courthouse in Philadelphia responding to anthrax scare (WTXF TV)

Executive Fire Chief Daniel Williams says crews responded to the federal court building in the city's historic district around 9:25 a.m. Wednesday. He says people have been evacuated from the second floor, but people on other floors remain in the building.

Williams says a letter was found, but he did not immediately know if any substance was found.

A spokeswoman for the Philadelphia Police Department says officers are also responding to the scene, but she did not immediately have additional information on what prompted the response.

(Copyright 2012 The Associated Press. All Rights Reserved)