Authorities rushed to the Brown Deer Pick ‘n Save grocery store on Green Bay Road due to a substance spill reported before noon on Friday.North Shore Fire and Rescue said they were dispatched around 11:56 a.m.Upon arrival, the substance was identified as mercury; however, the source of the mercury found inside a trash can remains unknown. North Shore Fire and Rescue says crews remained on scene for around seven hours.Store employees responsible for cleaning and garbage collection noticed the spill and reported it to the authorities.Approximately 20 store employees were on-site during the incident and were evaluated by paramedics as a precautionary measure. WATCH: News Chopper 12 overflies Pick N Save hazmat situationParamedics utilized a device capable of detecting mercury levels within an individual’s system. One employee showed a higher level of mercury exposure than what is considered normal. The affected employee is expected to undergo retesting.North Shore Fire Department …