NEVADA CITY (CBS13) — Police in Nevada Ciy are sounding the alarm over potential violent protests advertised on social media.

The department took to social media Tuesday, sharing the virtual flyers, some of which have detailed instructions on how to prevent officers from making arrests, by surrounding them in groups.

Police say some peaceful events were planned for the weekend but were postponed when investigators showed them the posts.

Last month, the Nevada City Police Department was criticized for not doing enough to stop a violent clash at a Black Lives Matter protest. The department admitted they were not prepared and said several arrests have been made since.

READ MORE: Nevada City Counter-Protester Arrested After Violence At Black Lives Matter Protest