A chemical reaction caused the SF State Police Station to be evacuated Thursday evening after University police used a testing kit to identify a substance they obtained on a call, according to University spokeswoman Ellen Griffin.

The initial reaction occurred at 4:45 p.m., prompting about five fire trucks to arrive at the scene and officials marked off the area directly in front of the police station.

"When the substances combined, it caused an unexpected reaction," Griffin said.

Neither Griffin nor Deputy Police Chief Reggie Parson could confirm the substance but an industrial hygienist will perform preliminary testing on the materials.

Paramedics arrived on the scene and examined five people but there were no injuries. One was sent to a hospital for further evaluation, three were determined fine and one is still pending in triage.

Officials asked all people not exposed to the unknown substance to keep away from the affected area. However, the situation is now contained.

The Library Annex and adjacent buildings were not evacuated and are still open to students.