A stage collapsed during a powerful storm at the Indiana State Fair on Saturday, sending steel scaffolding into the terrified crowd and killing at least five people awaiting a performance by the country band Sugarland.

The collapse came moments after an announcer warned of the advancing storm and gave instructions on what to do in event of an evacuation. Witnesses said a wall of dirt, dust and rain blew up quickly like a dust bowl and a burst of high wind toppled the rigging. People ran, screaming and shouting, desperate to get out of the way.

Afterward, hundreds of concert-goers rushed amid the chaos to tend to the injured, many trying to lift heavy beams, lights and other equipment that blew onto the crowd. Witnesses said many of the injured were in the VIP section closest to the stage, known as the "Sugar Pit." Emergency crews set up a triage center in a tunnel below the grandstand at the Indianapolis fairgrounds.

Indiana State Police 1st Sgt David Bursten said Sunday that four people died when the collapse happened and a fifth person died overnight at a hospital. At least 45 people were injured and treated at hospitals. Bursten said the injuries ranged from cuts and scrapes to "very serious injuries."

At least 18 people were taken to Wishard Memorial Hospital with problems ranging from head injuries and bone fractures to lacerations and other cuts and bruises, hospital spokesman Todd Harper said. He said those injuries were not life-threatening and conditions ranged from fair to critical. One person treated there was a 7-year-old child, he said, but didn't elaborate further.

Indiana University Health said Sunday that 26 people were treated at its hospitals, including three at its children's hospital. It said 16 were brought from the fair by ambulance, and all but one of those patients remained hospitalized.

Fair officials canceled all activities Sunday. The fair, which runs through Aug. 21, was expected to resume Monday with a service honoring the victims, Bursten said.

The Iowa State Fair announced Sugarland and opening act Sara Bareilles had canceled their Sunday show there.

Sugarland lead singer Jennifer Nettles issued a statement Sunday saying the band is "stunned and heartbroken for the fans and their families in Indiana. We hold those injured in our prayers at this very sad time. There are no words. It is tragic."

Nettles and Kristian Bush have sold more than 8 million records performing as Sugarland.

Emergency personnel and fair officials had been monitoring the weather and preparations were being made to evacuate the facility because a severe storm was expected in the area around 9:15 p.m., Bursten said. But the storm hit just before 9 p.m., and a "significant gust of wind" struck the stage rigging that holds lights and other equipment before the evacuation plan was activated, he said.

"As we all know, weather can change in a very rapid period of time," he said.

Concert-goers said Bareilles had finished performing and the crowd was waiting for Sugarland to take the stage. They said an announcer alerted them that severe weather was possible and gave instructions on what to do if an evacuation was necessary. But the same announcer said concert organizers hoped the show would go on, and many fans stayed put.

The wind that toppled the rigging came just minutes after that announcement, fans said.

"It was like it was in slow motion," concert-goer Amy Weathers told the Indianapolis Star. "You couldn't believe it was actually happening."

Associated Press photographer Darron Cummings was in the audience shortly before the collapse. He said he and his companions sought shelter in a nearby barn after seeing dark clouds approaching.

"Then we heard screams. We heard people just come running," Cummings told the AP. "When you see dark clouds like that, if there's going to be bad weather, there's going to be mass chaos on leaving."

Witnesses told WTHR that dirt, dust, rain and wind came up the main thoroughfare of the fairgrounds just before the collapse.

"Panic kicked in when they seen the dust bowl coming in from the Midway," concert-goer Darryl Cox told the television station.

Another person at the concert, Emily Davis, told the station there was lightning and the sky got dark but it wasn't raining when the wind suddenly toppled the rigging.

"It was horrible, people were running and going crazy," she said.

Jessica Alsman told the AP the towering, metal stage scaffolding "kind of wobbled at first." Then pandemonium set in as it fell.

"As soon as we saw the wind gust, the wind was in our faces," Alsman said. She and three friends grabbed each other and formed a chain.

"You can't imagine _ we just thought it was going to rain or something," Alsman said.

The Marion County Coroner's office identified the five victims as 23-year-old Alina Bigjohny of Fort Wayne, 29-year-old Christina Santiago of Chicago, and three Indianapolis residents: 42-year-old Tammy Vandam, 49-year-old Glenn Goodrich and 51-year-old Nathan Byrd. It was Byrd who died overnight.

Indiana's position in the Midwest has long made it prone to volatile changes in weather. In April 2006, tornado-force winds hit Indianapolis just after thousands of people left a free outdoor concert by John Mellencamp held as part of the NCAA men's Final Four college basketball championship tournament.

And in May 2004, a tornado touched down south of the Indianapolis Motor Speedway, delaying the start of the Indianapolis 500 and forcing a nearly two-hour interruption in the race.

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Associated Press writer Caitlin R. King in Nashville, Tennessee, contributed to this report.