Jason Merritt, Getty Images
"I'm speechless and feel so helpless," Bareilles tweeted. "Please send love and prayers to Indianapolis tonight. My heart aches for the lives lost."
"We are all right," Sugarland tweeted. "We are praying for our fans, and the people of Indianapolis. We hope you'll join us. They need your strength."
Both Bareilles and Sugarland scrapped plans to perform Sunday night at the Iowa State Fair.
Saturday's collapse is the third in a series of similar mishaps this summer. Last month, Cheap Trick narrowly avoided injury when a stage at Canada's Cisco Ottawa Bluesfest came tumbling down. Two weeks ago, rain and heavy wind in Tulsa, Oklahoma, brought down the Flaming Lips' lighting rig, preventing the band from playing an outdoor show at the city's District Block Party.
Rescue crews in Indiana worked throughout the night, and the American Red Cross set up a website where survivors can list themselves as "safe and well."
Watch Footage of the Stage Collapse