Granite County's first positive case of COVID-19 was an employee at Gem Mountain, the sapphire mine near Philipsburg.
Out of caution, the mine located on Skalkaho Pass Road is closed through the end of the month.
Staff who were identified as close contacts to the positive case were tested on Thursday morning and those results are expected back this weekend.
They are now in self-quarantine, according to a Facebook post.
Gem Mountain also wrote they undertook the recommended sanitizing and safety measures while trying to enforce social distancing to the best of their abilities.
They say their priority now is the safety of staff, community, and customers.