(CNN) Pittsburgh police ordered its detectives to bring riot gear to work Thursday in anticipation of protests should President Donald Trump fire Special Counsel Robert Mueller.

Police Cmdr. Victor Joseph reportedly sent an email Wednesday, instructing Major Crimes detectives to bring full uniforms and riot gear to work "until further notice."

In the internal memo obtained by local media, Joseph said "there is a belief" Mueller may be fired, and "large-scale" protests are expected in the central business district within 24 hours if it happens.

"The protest would be semi-spontaneous and more than likely happen on short notice," the memo said. "Based on this information, beginning tomorrow, April 19, 2018, all Major Crimes detectives are required to bring a full uniform and any issued protective equipment (riot gear) with them to work until further notice."

Read More