Police are investigating after at least two dozen participants in the Santa Barbara Half Marathon ended up at the hospital on Sunday.

The Santa Barbara Police Department said in a statement it opened an investigation after receiving reports from Santa Barbara Cottage Hospital about multiple half-marathon participants seeking medical treatment for “unusual symptoms.”

Neither the hospital nor police have detailed the symptoms beyond calling them unusual.

Cottage Health said in a statement Sunday that it had a “larger than expected number of emergency visits … a number of them with similar symptoms of undetermined cause.”

Race organizers say they believe any illness is attributable to heat or dehydration.

Cottage Health said Monday that 25 participants arrived at its Santa Barbara and Goleta emergency rooms, and 18 had been discharged as of that morning.

The others were in stable condition, the company said in a statement.

A police spokesperson did not immediately respond to requests for comment Monday on the status of the investigation.

The temperature in Santa Barbara reached 80 degrees Fahrenheit (around 27 degrees Celsius) by 10 a.m., which is unusual for November, when high temperatures usually reach the lower to mid-70s, said Ryan Kitell, a meteorologist with the National Weather Service.

Roughly 7,500 people participated in the event, which spanned 13.1 miles (21.1 kilometers) along the Pacific Ocean and through the city’s downtown.

Event director David Monico said organizers transported 15 people from the medical tent to local hospitals. He said the event’s medical team treated numerous runners for dehydration and overheating both on the course and at the finish line.

“There was no unusual symptoms or anything outside of the norm for a half marathon or a marathon or some type of endurance event,” Monico said.