BROOKLYN PARK, Minn. (WCCO) – The phone number used to call in a threat of violence against Park Center High School Thursday has been linked to other national complaints of harassment and pranks, police said.

Authorities say two Brooklyn Park schools were placed on lockdown Thursday after an unspecified threat.

Brooklyn Center police say that just before noon, they received a phone call from a man threatening to commit an act of violence at Park Center High School. The number was later determined not to be local.

Authorities say because of the information the man provided, Park Center and Brooklyn Middle School were placed on lockdown. Several officers were dispatched to school property to provide security for the remainder of the day.

Police say there wasn’t a direct threat by the man to commit violence at any other school, but at least one officer was placed at every Brooklyn Park school as a precaution. The lockdown was lifted Thursday evening and classes resumed normally Friday.

Police say they have been conducting an extensive investigation, including serving numerous search warrants. The investigation is ongoing.