In scorching heat and high humidity, the Chicago Marathon took a deadly turn Sunday.

One runner died, at least 49 were hospitalized and thousands were denied the chance to cross the finish line in the race long known for its brisk fall temperatures and flat terrain.

Paul Gardiner, a runner from England, said the weather made for a "brutal" run.

"We were at about 18 miles and we heard they canceled it and that kind of sent a little bit of concern through the crowd," he said. "It's just it's impossible to run."

The 88-degree heat and sweltering humidity were so draining that organizers shut down the second half of the course 3 1/2 hours after the start.

About 10,000 of the 45,000 registered runners chose to not race in the heat despite more mist stations, cooling buses and water-soaked sponges, while another 10,934 started but didn't finish, officials said.

Kenya's Patrick Ivuti won, leaning at the finish line to edge Jaouad Gharib of Morocco by 0.05 seconds. Ethiopia's Berhane Adere rallied to successfully defend her women's title.

An autopsy is scheduled for Monday for Chad Schieber, 35, of Midland, Mich. He collapsed while running on the South Side and was pronounced dead shortly before 1 p.m. at a Veteran's Affairs hospital, the Cook County medical examiner's office.

"Obviously very sad news, and our thoughts and prayers are with the individual's family," said Shawn Platt, senior vice president of title sponsor LaSalle Bank.

George Chiampas, the race's medical director, said witnesses reported seeing Schieber collapse and become unresponsive. "It sounds like he lost his pulse very fast and died on the race course," Chiampas said.

There was another running death Sunday in Arlington, Va. An unidentified runner from Virginia died during the Army Ten-Miler, collapsing near the finish at the Pentagon. The race started in 70-degree heat and high humidity.

These were record temperatures for the Chicago Marathon, topping the mark of 84 degrees in 1979. Runners were diverted to the starting area, where they were provided with medical attention and cooling misters. Shortages of water and energy drinks were reported along the 26.2-mile route.

Race director Carey Pinkowski said organizers were concerned that emergency medical personnel wouldn't be able to keep up with heat-related injuries.

"We were seeing a high rate of people that were struggling," Pinkowski said. "If you were out there at 1 o'clock, it was a hot sun. It was like a summer day. It was just a brutally hot day."

At first, organizers hoped those who passed the halfway mark could complete the run. But eventually even those recreational runners were told to turn back.

Still, some runners persevered, although organizers said they didn't know how many completed the course. Helicopters hovered over the race course while police officers shouted through a bullhorn and warned runners to slow down and walk.

Lori Kaufman, a runner from St. Louis, said she was told to start walking at mile 14. She said the fire department turned on hydrants to hose people down along the course.

Ivuti, competing in only his second major marathon, was timed in 2 hours, 11 minutes, 11 seconds in the closest finish in the race's history. He was the fifth straight Kenyan to win the race.

"I had never seen a marathon finish up close that was like that," head referee Pat Savage said. "This was really close, but at the same time you could see that one man was ahead of the other."

Adere finished in 2:33:49 after passing a surprised Adriana Pirtea, who had a comfortable 30-second lead after 24.8 miles.

Ivuti and Gharib surged ahead of defending champion Robert Cheruiyot and Daniel Njenga at the 22-mile mark to make it a two-man race. Gharib led for much of the final 4 miles before Ivuti made a push on the final mile.

"One thing I had in my mind was that everybody is going to face the same heat," Ivuti said. "I had no problem with that because everybody was going through the same thing as me."

The duo traded leads on the stretch run down Columbus Avenue before Ivuti's final push at the line. The race was so close that it took organizers several minutes to determine the winner.

Njenga finished third and Cheruiyot fourth. Cheruiyot was in position to contend but stomach craps forced him to drop back after 22 miles. Cheruiyot, who last year slipped on the finish line and banged his head on the pavement as he raised his hands to celebrate, finished in 2:16:13.

Pirtea waved to the crowd as she listlessly approached the finish line. But a final push on the last mile by Adere caught the Romanian in the final stretch.

"At 40 (kilometers), I could see she was going slowly," Adere said. "I knew if I started working from that point on, there was a possibility to catch her."

Pirtea tried to sprint toward the finish line, but finished three seconds behind.

"I had tears," Pirtea said.

American Kate O'Neill finished third and Liz Yelling was fourth.