A batch of cake mix sent in the mail triggered an evacuation this morning of the administration building at the House of Correction, a medium and minimum security jail in the Philadelphia Prison System.

The powdery cake mix was found in the inmates' incoming mail, which was being inspected by a correctional officer.

The discovery prompted a call for Hazmat and Fire Department teams to respond, which prison officials said is protocol. The House of Correction is in the 8000 block of State Road.

The administration building, including the warden and deputy warden's offices, was evacuated.

The administration offices and the inmate housing are separated by a long corridor, prison officials said, and no inmates were removed from the jail.

The substance was determined to be a cake mix and the building was reopened about 12:30 p.m., officials said.

Contact staff writer Troy Graham at 215-854-2730 or tgraham@phillynews.com.