GREEN BAY, Wis. (AP) — A Wisconsin marathon was halted Sunday after several runners and walkers experienced heat-related problems and required medical attention.

Cellcom Green Bay Marathon director Sean Ryan told The Associated Press officials knew temperatures would climb when the race started at 7 a.m. but hoped a combination of wind, medical resources, ice and water stops would help keep problems in check.

“The temperatures climbed rapidly,” Ryan said. “Within a matter of hours, the situation began to overwhelm medical resources.”

The race was shut down at 9:35 a.m. A total of 7,411 people started the marathon and half-marathon, and 49 percent finished before the race was stopped, most of them in the half-marathon. Only 10 marathoners finished with official times, Ryan said.

He did not have immediate information on the number of people affected by heat. But the Green Bay Press-Gazette reported that an hour after the race was stopped, emergency rooms at St. Mary’s Hospital Medical Center and St. Vincent Hospital were full with runners. WLUK-TV reported that those needing medical attention were directed to other hospitals.

Marathon media coordinator Tammy Vandenbusch said once the course was shut down, runners were urged to get on shuttle buses, but some kept running.

“They are being strongly urged to stop,” she said.

J.P. Conroy, a half-marathoner from Winona, Minn., told the Press Gazette he stopped running and started walking.

“I didn’t want to be that person. I didn’t want to take a chance,” he said. “People were lying down with ice packs on them on Mile 7 and around Mile 11.”

The newspaper reported that David Tuwei won the men’s full marathon in 2 hours, 27 minutes, 11 seconds.

The National Weather Service predicted a high of 82 degrees in Green Bay on Sunday. The temperature was 70 degrees with 63 percent humidity when the race started.

“It was a tough day for running,” Vandenbusch said.