Haywood died at Medical Center of Arlington, hospital spokeswoman Diane Stout said.
"The cause of death at this time is unknown," she told The Associated Press. She said she doesn't know what Haywood was being treated for.
Haywood was taken to the hospital early Saturday after waking up feeling ill and vomiting, Iowa State director of media relationsTom Kroeschell told The Associated Press on Sunday. Kroeschell said he got the information about the former Cyclones player from the school's football coach, Dan McCarney.
Haywood participated in the Cowboys' three-day minicamp last week and was expected to compete for a roster spot at halfback.
Haywood, an undrafted free agent, was on the Cowboys' practice squad last season.
The referee reviewed the winning goal to determine whether the puck had completely crossed the goal line.
International Ice Hockey Federation officials watched the replay from seven different angles. Officials said on the best frame, the puck was "barely but visibly" inside the goal line.
Canada went undefeated during the tournament and added the world title to its Olympic gold medal.
He'll be toasted by horsemen, breeders and politicians in Albany for being the first New York-bred colt to win the Kentucky Derby. Everyone will be there, except winning jockey Jose Santos.
Accompanied by his lawyer, Santos will be in Louisville for a hearing with Churchill Downs stewards, who spent the weekend examining a photo of him possibly holding something in his hand besides his whip when he crossed the finish line.
The inquiry will focus "most particularly on the actions" of Santos at the race, said chief steward Bernie Hettel, who will be joined by stewards Rick Leigh and Jack Middleton.
Funny Cide, a 12-1 shot, beat favorite Empire Maker by 1 3/4 lengths to become the first gelding to win the Derby since 1929.
Dominguez was unable to find a way around Bourdais on the 154th and final lap. They drove side by side through the final two turns, with Bourdais on the inside. Michel Jourdain Jr. finished third.
Bourdais, driving a Newman-Hass car, started from the pole for the third time in five races. He won last Monday on the road course at England's Brands Hatch, his first victory in Champ Cars.
Brazil's Bruno Junqueira was fourth, followed by Spain's Oriol Servia and England's Darren Manning.
Canada's Paul Tracy finished 13th and picked up a point to maintain the overall lead with 66 points. Junqueira also has 66 but Tracy leads because he has won three races this season.
Mantilla earned him $459,000 and Federer won $229,000.
The fourth-seeded Federer made numerous mistakes on an uncomfortably hot day, but both players established themselves in this major tuneup for the French Open, which starts May 26.
Justine Henin-Hardenne fought off three match points and won the German Open for the second straight year, defeating Kim Clijsters 6-4, 4-6, 7-5 Sunday in an all-Belgian final.
Henin-Hardenne won her third title of the year and became the first player in nine years to retain her championship at this important clay-court tuneup for this month's French Open.