A merry-go-round collapsed at a zoo in southern Spain on Saturday, injuring 18 people, mostly children, officials said.

Two of the 15 injured children suffered serious injuries and were taken to a hospital after the accident at the Guillena Zoo (search) in Seville (search), said Francisco Javier Cuberta, a city health official.

"The central axle of the machine snapped and it collapsed," said Guillena Mayor Jose Padilla (search), speaking on CNN+ television.

One of the children suffered a serious leg injury, state news agency Efe reported.

Media reports said more than 30 children and three adults were on the fairground attraction when it collapsed. Some of the injured were trapped under debris.

The ride was built in 2001 and had passed all of its annual safety inspections, with the last in July, Padilla said.

Police are to investigate the cause of the accident.