Four paramedics who worked at the Bonnaroo Music & Arts Festival in Manchester, Tennessee, this past weekend have been hospitalized for potential carbon-monoxide poisoning, according to Coffee County Sheriff’s Office spokesman Lucky Knott.

Knott said the exhaust outlet from a generator used to power the paramedics’ RV was apparently blocked. One of the paramedics awoke Monday and was able to call for help. One of the four was taken to a nearby hospital; the other three were airlifted to hospitals.

Knott said none of the four hospitalized paramedics is employed by Coffee County EMS.

According to figures released by the sheriff’s office, as of Monday, at least 37 Bonnaroo attendees had been hospitalized, and there was one fatality. Friday morning, the body of 32-year-old Michael Donivan Craddock, Jr. was found in his car at one of the festival campsites.