Health officials are testing stool samples from runners in the Rock ‘n’ Roll Marathon in Las Vegas who say water passed out during the race made them sick.

Southern Nevada Health District officials are testing for stomach flu and other diseases, and expect results later this week. An online survey they’ve posted has already drawn responses from more than 800 participants.

The Dec. 4 event drew about 44,000 participants, who paid up to $179 to run a half or full marathon. Dozens of runners posted stories on Facebook about nausea, vomiting and severe stomach pain after the race.

Race organizers had filled plastic-lined garbage cans with hydrant water, which was used to fill cups offered to racers along the course – a standard practice, marathon officials say. Volunteers wearing plastic gloves dipped cups into the garbage cans before passing the water to runners.

While some runners complained that the water tasted odd or unclean, Las Vegas Valley Water District officials say the hydrant water was tested and found to be safe days before the race.