Five employees at Sydney's Easter Show have been injured after reportedly riding a giant slide early on Sunday morning, while the ride was closed.

Emergency services were called to Sydney Olympic Park shortly after midnight.

Police said three men and two women were injured, including a 22-year-old woman who broke both legs and a 60-year-old man who sustained broken ribs and internal bleeding.

The man and woman were taken to Westmead Hospital, while two others were treated at Concord Hospital.

The fifth man was treated at the scene.

Police said all five were employed at the show and that the ride was closed at the time of the incident.

Sydney Royal Easter Show officials said the super slide had been closed because of wet weather.

On Sunday the show's chief operating officer, Michael Collins, said those involved were contractors.

"I'm told they were heading towards the gate, there would have been security down there, obviously they've missed them. I guess but we'll find that out today," he said.

The amusement, known as the Super Slide, was secured on Sunday while Work Cover investigators examined the site.

The WorkCover investigation identified a breach and a notice was issued to the amusement device owner to prevent unauthorised access after hours.

The police investigation continues.