NEW YORK—Officials from New York Road Runners stripped American Meb Keflezighi of his 2009 ING New York City Marathon victory Wednesday after a blood sample taken from his fetlock was found to contain high levels of performance-enhancing horse.

"Meb's fellow competitors voiced their doubts about him immediately after the event," NYRR president Mary Wittenberg said. "In addition to his remarkable speed, unusual race-day height, and distinctive 'clip-clop' gait, Keflezighi's frequent nickering caused the other runners to speculate that he may have been using a horse in some fashion."

Added Wittenberg, "Also, just before the start, he lifted up his tail and loudly deposited a 9-inch-high pile of steaming fecal matter on the pavement, an unusual occurrence even in the world of long-distance running."

Keflezighi finished the race in 48 minutes and 12 seconds, easily setting a new world record and defeating his nearest competitor by one hour and 20 minutes.

Course workers, spectators, and event sponsors have all presented damaging evidence pointing toward Keflezighi's use of equine enhancements. Volunteers working refreshment tables during the race said Keflezighi took water only twice—at miles nine and 17—consuming roughly 10 gallons each time, and was the only professional runner in the men's event to request an oat, carrot, and sugar lump station. In addition, a spokesman for Nike told reporters the company provided Keflezighi with six shoes for the marathon, four of which required special construction before being nailed onto his feet.

Hundreds of people who watched the race have also come forward with photographs showing Keflezighi mounted atop what experts now believe to be a 2-to-4-year-old chestnut-brown thoroughbred.

"Come to think of it, he was moving at a pace that didn't seem human," spectator Mark Rolland said. "And when the marathon was over, the American flag they tried to drape around him didn't even come close to fitting around his body."

"Last year he was just this small guy, but when he showed up to the starting line this year, his neck and head were noticeably thicker," said David Willey, editor in chief of Runner's World magazine. "He looked like he had put on at least a half ton of muscle."

The NYRR's Wittenberg said during a postrace press conference that if the evidence proves conclusively that Keflezighi used a horse to improve his speed and endurance, it would not only have a severe impact on his career, but could cast doubt on the whole culture of long-distance running.

"It may seem hard to believe this could happen, especially at this level," said Dr. Raymond Prentiss, a medical adviser for USA Track & Field. "But people are so eager to believe in man's ability to push the boundaries of achievement that they blind themselves to a competitor who looks a little too strong, runs a mile a few minutes faster, and stands a few hands taller than the competition."

"In Keflezighi's case, we ignored what his rapidly improving times, flowing mane, and shapely withers were trying to tell us until it was too late," Prentiss added. "The fact that he was spending an hour after each event currycombing should have been a major tip-off."

As of press time, Keflezighi is cooperating with the sanctioning bodies and has returned the $170,000 he was awarded for the victory. He has also surrendered his racing singlet and shorts, saddle, saddle blanket, and bridle for further inspection and testing by technical personnel. Officials with the World Marathon Majors series said that Keflezighi will likely be banned from future races, including Boston, Chicago, the 2010 Belmont Stakes, and Berlin.

In light of the discovery, marathon officials are taking a closer look at many of the entrants in this year's race, including British runner Paula Radcliffe, a former winner who placed a tearful fourth in the women's event after fracturing her cannon bone and had to be put down mere minutes after finishing.