Four people have been killed and 40 hospitalised in Indianapolis after stage rigging collapsed during a storm at the Indiana State Fair.
The incident occurred as thousands of people gathered for a concert by Grammy-award winning female country music duo Sugarland, The Indianapolis Star reported.
A strong wind gust hit about 9pm local time, between the opening and main acts, which caused stage rigging and the roof to collapse and fall onto the crowd.
Indiana State Police Sgt. Rich Myers confirmed to FOX News Channel that four people were killed. An earlier police statement had said there were three deaths. Authorities said a further update would be provided soon.
The 40 people who were injured had been taken to the Methodist and Wishard hospitals, police said. Their injuries ranged from bruises to fractures and head trauma, WTHR-TV reported, adding that some of the patients were children.
Natalie Prater, a paediatric nurse who helped the injured, said she and her husband were walking away from the stage when the collapse occurred.
"Then we heard things popping and we took off running," she said. "People were pushing. We turned around and saw the stage collapsing. Then we ran back, hopped over rafters and went to help as many people as we possibly can."
Cadaver dogs are being used by police officers to search the rubble for anyone else who could be trapped, WISH-TV reported.
Witnesses said the violent wind gusts hit the fairground out of the blue, just prior to the incident.
According to one reporter from the Star who was at the venue, less than 30 minutes before the wind gust hit the opening act, Sara Bareilles, finished her set by commenting what a beautiful night it was.
Witness Emily Davis told WTHR-TV the crowd had been told it would be evacuated if the storm grew worse and a short time later the stage collapsed.
Indianapolis Mayor Greg Ballard praised the work of emergency service staff at the scene.
"Everything has been very well coordinated to respond to this event," Ballard said.
Earlier Sugarland posted a message on Twitter to say that they were safe.
"We are all right. We are praying for our fans, and the people of Indianapolis. We hope you'll join us. They need your strength," they said.
The Indiana State Fair is 6th oldest State Fair in US, originating in 1852.