GEORGE, Wash. — More than 160 cases of COVID-19 have been confirmed so far among people who attended the Watershed Music Festival at the Gorge Amphitheatre in central Washington.

More than 20,000 fans packed the Gorge, in George, for the three-day outdoor country music festival in late July, the Seattle Times reported.

The Grant County Health District said Friday the cases are tied to residents in counties including King, Grant, Pierce, Skagit, Kittitas, Okanogan, Whatcom, Kitsap, San Juan, Lincoln and Stevens. There’s also one case tied to an Oregon resident.

Officials expect more cases associated with the festival to be confirmed in the coming days and investigators are working with those who have tested positive to identify other cases.

Public Health officials urge people who attended the festival to self-quarantine and get tested for the virus. On average, symptoms of the virus develop five to six days after exposure, but the incubation period can be as long as 14 days, officials said.

In eastern Oregon, Umatilla County Public Health officials have tied at least 66 COVID-19 cases to the outdoor Pendleton Whiskey Music Fest on July 10. Sixty-one of the people who tested positive were unvaccinated, officials said.