A South Dakota motorcycle rally attended by nearly half a million people earlier this year resulted in at least 86 cases of COVID-19 among residents of Minnesota, including one death, according to a report released Friday by the Centers for Disease Control and Prevention.

The report, which looked to find the impact of the rally on a neighboring state, found that of the 86 identified cases among Minnesotans, 35 had not gone to the event but were contacts of people who did. 

About one-third of Minnesota counties had a case associated with Sturgis rally, which took place over a 10-day period in August with no social distancing or mask requirements.

The findings show the importance of wearing masks and following social distancing rules and other recommendations from public health officials in stopping the spread of COVID-19, the authors of the report wrote. 

“These findings highlight the far-reaching effects that gatherings in one area might have on another area,” the authors wrote. 

“The motorcycle rally was held in a neighboring state that did not have policies regarding event size and mask use, underscoring the implications of policies within and across jurisdictions.”

The authors noted that the number of cases among Minnesotans is likely an undercount because some people may not have been tested or did not participate in interviews with public health officials. 

The report did not look at how many people in South Dakota became sick.

South Dakota Gov. Kristi Noem (R), who still does not mandate masks in her state, supported the rally taking place.

South Dakota now has one of the largest and deadliest COVID-19 outbreaks in the country relative to population size.