MIAMI -- Two of the three children tossed onto a South Florida beach from a bounce house sent flying by a waterspout have been sent home from a hospital with minor injuries, hours after the inflatable was sent airborne above palm trees and a four-lane road, police said.

Authorities said the two children were sent home Monday and a third child was in stable condition and being held overnight for observation after the waterspout lifted up the bounce house from the beach.

No pedestrians or vehicles were hit when that and a second, unoccupied bounce house went flying, police added.

All three children were quickly thrown to the beach Monday as the bounce houses were uprooted and both inflatables then crashed in a parking lot across a state road, police said. The injured children were alert and conscious when they were taken to a hospital, Fort Lauderdale Police spokesman Keven Dupree said.

A police statement Monday evening said two of the children were treated for minor fractures and released while the third was stable at Broward Health Medical Center. Their identities were not released.

Police said no vehicles or pedestrians were hit by the bounce houses.

Video on local television stations showed the waterspout -- a whirling column of air and water mist -- moving from the ocean onto the sand of Fort Lauderdale beach, tossing a canopy and rolling one of the bounce houses before lifting it into the air.

The house flew above the tree line, but the children fell out when it first flipped over the beach, Dupree said. "They were immediately dropped out of the bounce house onto the sand," he said.

Both bounce houses had been secured to a basketball court as part of a city-sponsored family activity zone set up for a Memorial Day holiday event. The waterspout snapped a concrete pole holding a basketball hoop.

Burt Osteen, a 37-year-old flooring installer from Fort Lauderdale, and his family dove to the sand on their stomachs as they saw the waterspout spinning toward them.

"It came right over us. We laid on the ground; we were right in front of the bounce house. We watched it pick up the bounce house and snap a basketball hoop," Osteen said.

He barely felt anything, though, when the waterspout passed over them. The tablecloths on nearby picnic tables weren't even disturbed by the wind, he said.

"The only thing was the sand, getting stung by the sand," he said.

Unlike tornadoes, waterspouts don't need thunderstorms for their funnel clouds to form.

On Monday afternoon, a band of clouds moving in from the ocean had winds favourable for waterspout formation, said Jeral Estupinan, a meteorologist with the National Weather Service in Miami.

"It developed very close to the coastline and moved onshore, and it dissipated very quickly onshore, like any other waterspout," Estupinan said.