An investigation has today been launched after two circus performers were injured when a motorcycle stunt went wrong during a performance in Chantry Park, Ipswich.

Ipswich Star: The scene at Uncle Sam's Great American Circus in Chantry ParkThe scene at Uncle Sam's Great American Circus in Chantry Park (Image: Archant)

The stunt riders from Uncle Sam’s Great American Circus were performing the motorcycle thunderball to a packed big top when disaster struck yesterday afternoon.

Audience members were evacuated from the circus while medics from the East Anglian Air Ambulance and paramedics from the East of England Ambulance Service (EEAST) treated the men.

A joint investigation between Suffolk police and the Health and Safety Executive has now been launched.

A Suffolk police spokesman said officers were called to the Hadleigh Road side of Chantry Park by EEAST just after 5pm to reports that two motorcyclists had collided while taking part in the stunt show.

This morning a spokesman said both riders were still in Ipswich Hospital.

Michael Nanton, 49, and Sue Padmore, 51, from Ipswich, were among the crowds at the circus show when the accident happened just before the interval.

Mr Nanton said: “It was scary to see it happen. The bikes crashed, the motorcyclists fell and landed underneath the bikes.

“The organisers asked if anyone in the audience had medical training or was a paramedic to assist them.

“Then we were evacuated straight away and they gave people half their money back.”

The thunderball stunt involves motorcyclists riding around at speed in a small spherical cage performing tricks while defying gravity.

One eyewitness, who did not wish to be named, was at the circus with his fiancé and five-year-old daughter, said the show lasted about 20 minutes before the accident happened.

He added: “Lots of people were left shocked and upset, especially the children.”

The riders were taken to Ipswich Hospital by land ambulance with air ambulance medics assisting.

An EEAST spokesman said two ambulances, a response car and the air ambulance were called to the scene just after 5pm.

He added: “One rider suffered a head injury and one with upper body and leg injuries.

“Both were fully conscious and neither were critical. Neither are thought to be in a life-threatening situation.”

An update on the circus’ Facebook page last night said: “To all our audience from the 4.30pm show today, we would just like to thank you all for your support during the accident with our thunderball riders.

“We have just had an update from Ipswich Hospital and both are doing well and stable, soon to be on the mend.

“We want to thank you for your understanding as we had to cut short the show, however our rider’s safety was, and is, our main priority.

“We will pass on all your kind words and well wishes and keep all posted on any updates.”

A spokesman for Ipswich Borough Council, which operates Chantry Park, said: “We are aware of this horrible accident and we wish those involved a full recovery.

“The police are in charge of the scene and have sealed off part of the park.”

A police investigation into the incident is ongoing and anyone with information is asked to contact Suffolk police on 101.