Santa Barbara police and local health officials are investigating after 26 runners became ill near the end of the Santa Barbara Half Marathon on Sunday, sending numerous participants to the hospital.

The race had nearly 5,000 finishers and was held in relatively warm conditions. The temperature was a modest 62 degrees at the start but quickly climbed into the mid-80s by the time the final runners crossed the finish line hours later.

Although the weather might have been comfortable for spectators, research suggests optimal temperatures for long-distance races range from 35 to 55 degrees Fahrenheit.

Race organizers said in a statement there is no indication the illnesses were caused by anything beyond exertion associated with an endurance event.

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“During and since the event, we have worked closely with local authorities to provide as much information and access as possible. At this point, we have no additional information to suggest that the issues some of the participants experienced were caused by anything other than endurance event exertion-related symptoms,” the race said.

The Santa Barbara County Health Department released a statement agreeing with the race’s assessment.

“Runners began experiencing symptoms consistent with heat-related illness,” the department said. “The medical incident appears to be an isolated event connected directly to race participation and the heat. There is no indication of a broader public health concern or ongoing risk to the community.”

However, one hospitalized runner questioned that explanation.

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“It is awfully suspicious,” the participant told KEYT-TV. “We had people saying they were hallucinating. I was unconscious for almost an hour. None of us remember running for a portion of it. I am not too familiar with heat exhaustion, but I have never seen anyone not remembering a long portion of their run.”

Health officials said there was no evidence that water or other supplies along the course had been tampered with.

“All water supplies and related materials inspected were observed to be clean, properly packaged, unopened, and stored in sanitary conditions. No findings were identified during either inspection,” the health department said.