Updated: Sunday, Aug. 14, 2011 -- 1:15 p.m. ET

A fifth person has died after Saturday's (Aug. 13) stage collapse at a Sugarland concert at the Indiana State Fair in Indianapolis, authorities confirmed Sunday morning.

Sugarland's Jennifer Nettles and Kristian Bush were not onstage or injured when a wind gust toppled a canopy, scaffolding and other stage rigging, but they have canceled their Sunday concert scheduled at the Iowa State Fair in Des Moines.

At least 45 people were transported to area hospitals after the towering metal structure fell into the crowd. The Indiana Occupational Safety and Health Administration has launched an investigation into the design and construction of the stage, although Indiana Gov. Mitch Daniels described the incident as a "freakish accident."

Those who died at the scene have been identified as Tammy Vandam, 42, of Wanatah, Ind.; Glenn Goodrich, 49, of Indianapolis; Alina Bigjohny, 23, of Fort Wayne, Ind.; and Christina Santiago, 29, Chicago. Nathan Byrd, 51, of Indianapolis, who was part of the local stage crew working at the concert, died Sunday morning at a local hospital.

Several of the survivors are being treated for serious injuries, and Indiana State Police 1st Sgt. Dave Bursten said there's still a possibility of additional fatalities.

Singer-songwriter Sara Bareilles had completed her opening set at the concert, but Sugarland had not yet begun their headlining performance when the accident occurred. Around 8:45 p.m., an announcement was made that a storm with high winds was headed toward the area. Some 15,000 fans attending the concert were told to be prepared to leave the outdoor venue and seek shelter at a nearby arena.

WISH-TV in Indianapolis said it could not be confirmed that a tornado hit the area, but winds in excess of 60 miles per hour were reported.

During a Sunday morning press conference, Daniels said fair officials followed the proper safety procedures to prepare for a storm, but the heavy winds arrived 30 minutes earlier than predicted. He said law enforcement personnel and private citizens attending the concert worked together to move the debris and assist the injured.

"What you saw last night was a display of best qualities, both public and private, of Hoosiers," the governor said.

Immediately following the accident, Sugarland sent a Twitter message that they are OK and to pray for the people who were affected by the stage collapse.

Sugarland vocalist Jennifer Nettles later issued a statement.

"We are stunned and heartbroken for the fans and their families in Indiana," she said. "We hold those injured in our prayers at this very sad time. There are no words. It is tragic."

In a Twitter message, Bareilles wrote, "I'm speechless and feel so helpless. Please send love and prayers to Indianapolis tonight. My heart aches for the lives lost."

All activities at the fair have been canceled on Sunday, but the event will reopen Monday with a memorial service for those killed and injured. Janet Jackson is scheduled to resume the concert series on Wednesday, followed by Train and Maroon 5 on Thursday. Lady Antebellum and Brett Eldredge are set to perform Friday.

Sugarland's tour is expected to resume Thursday in Albuquerque, N.M.