Between 70 and 100 kids and young adults were in attendance at the June 27 gathering, sources told the station.
The Wetzel-Tyler County Health Department says 16 people from Wetzel County and five people from Tyler county have tested positive for COVID-19 after attending the party.
Officials says they expect more positive cases.
The health department has been in the process of contact tracing and testing from the party and also wanted to note that many of the individuals are asymptomatic.
Those who attended the party are being urged to go to the free COVID-19 testing sites in Marshall County. People are now asked to wear a mask if out in public or in social gatherings.
Extracurricular activities have been shut down for two weeks in both counties.