A two-year-old boy is among four people killed after a woman drove into a crowd during a homecoming parade at Oklahoma State University.

Witnesses described how bodies were thrown dozens of feet into the air when the Hyundai Elantra slammed into the crowd in Stillwater, near Oklahoma City.

The vehicle crashed through barricades and struck an unmanned police motorcycle before ploughing into spectators.

The driver, 25-year-old Adacia Avery Chambers, has been taken into custody on suspicion of driving while under the influence of alcohol.

The suspect's father, Floyd Chambers, told the The Oklahoman newspaper that he learned about the incident via social media and was stunned.

"I can't figure this out. This is not the person that's my daughter," he said.

"I can't imagine alcohol being involved. She is not an alcoholic that I'm aware of."

Representatives for OU Medical Center in Oklahoma City said the hospital treated eight victims from the crash, five of them children.

One of those patients, a two-year-old boy, later died.

A further 40 patients were treated at the Stillwater Medical Centre.

Dave Kapple from Houston told the Stillwater News Press that he and his son were about 10ft away from the crash site.

"We heard somebody scream, 'Look out!.' (He) ploughed through a police motorcycle, and then a crowd of people," he said.

"People were flying everywhere."

Konda Walker, from Anchorage, Alaska, was also nearby. She told the News Press: "At first we thought it was part of the show. People were flying 30ft into the air like rag dolls."

Geoff Haxton, who went to the parade with his children, said: "I just saw smoke and saw the panic in people's faces as they ran away from the scene."

Oklahoma State University chose not to cancel its homecoming football game in the wake of the accident.

The game went ahead as planned against Kansas, and was dedicated to the victims.

"We are shocked and heartbroken by this horrible tragedy," said the school's president, V Burns Hargis.

"The Oklahoma State University Homecoming parade is the most wholesome of events and to have it marred in such a way is incomprehensible."