GATLINBURG (AP) — Tennessee authorities say E. coli bacteria caused the sickness that affected more than 500 people at a zipline attraction.

Gail Harmon is the assistant director of the East Tennessee Region Health Department. Harmon tells news outlets well water samples from CLIMB Works Zip Line Canopy Tour in Gatlinburg are headed to Nashville after initial tests found E. coli bacteria and total coliforms. Using CLIMB Works' online sales records to email 2,901 surveys to patrons, the Tennessee Department of Health learned that 548 of the 808 respondents reported illness.

The health department says the respondents visited CLIMB Works between mid-June and early July and are in multiple states. CLIMB Works has cooperated with the health department and is offering refunds to those sickened.