(CNN) -- An Independence Day parade in Iowa descended into chaos when when two horses went out of control and took their wagon with them, running into crowds of celebrants and leaving more than 20 people injured, according to authorities.
A woman injured in the incident died Sunday evening, police said.
It happened at the Bellevue Heritage Day Celebration Parade in Bellevue, Iowa, on the state's eastern border with Illinois.
Fire Chief Chris Rowling told CNN that emergency officials responded to a call that came in just before noon, about a "mass casualty incident" at the annual Fourth of July parade.
Rowling said two horses pulling a wagon went out of control along the parade route. They ran with the wagon for about six blocks, hitting numerous children and adults.
A total of 24 people were taken to hospitals in the area. The injuries ranged from abrasions to fractures to collapsed lungs. Five people were in critical condition and five were in severe condition, while 14 people had injuries considered minor, Rowling said.
Rowling added that the injured ranged in age from 2 to 62, with more than half being under the age of 12.
Brent Roling with the Bellevue police department said a 60-year-old woman died hours after the incident at a hospital in Iowa City.
Fire Chief Rowling said one of the horses hitched to the wagon dislodged the bridle of the other horse, compromising the driver's ability to control them both.
Iowa Gov. Chet Culver issued a statement on the incident, saying his "thoughts and prayers" were with the injured and the town.
"I am especially saddened because the accident occurred during the events celebrating Independence Day, which is a day that should be filled with pride and joy for all Iowans and Americans," Culber said, adding that he thanked the spectators who aided the injured, and the emergency responders at the scene.