The country music duo of Jennifer Nettles and Kristian Bush has been named in the suit, which was filed Tuesday, along with producers and other organizers of the concert, according the the Associated Press.
Sugarland has not released a statement.
Several other lawsuits have already been filed and the incident remains under investigation.
Earlier this month a relief fund set up began paying out $531,500 to 26 of those killed and people hospitalized. Over $1 million in total has been raised for the families of the seven people who were killed in the stage rigging collapse at a concert by the group Sugarland on August 13 and to people hospitalized due to injuries.
Indiana Governor Mitch Daniels has asked for several staffers to be assigned to the State Fair Commission to assist in the fact finding and documentation procurement aspect of an investigation into the incident.
An outside engineering company has been hired to conduct a structural investigation and emergency preparedness consultants have been brought in to analyze the state fair's disaster preparedness and response to the collapse.
Singer Sara Bareilles had just finished her set on the outdoor stage when 60 mile-per-hour winds took the stage down around 9 p.m. Saturday.
"I'm speechless and feel so helpless," Bareilles said on her Twitter page. "My heart aches for the lives lost."
Sugarland, the show's headliner, was to take the stage next.
"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," the band tweeted.
Indianapolis Department of Public Safety confirmed 44 people were injured and 7 people were killed.
"A big gust of wind came through. You could see a lot of people panicking. All the scaffolding and speakers -- all that came crashing down -- and the whole stand just collapsed," said Aaron Richman, who witnessed the collapse at the Indiana State Fairgrounds in Indianapolis.
Concertgoers and rescuers were holding up parts of the collapsed stage that fell into the standing area below to help anyone who might be trapped, eyewitnesses said.
David Lindquist, music critic for the Indianapolis Star, tweeted: "Tragedy at fair concert. Entire stage collapses on track."
He also tweeted: "Perhaps a dozen injured people have been removed from track on stretcher-type boards."
The National Weather Service issued a hazardous weather alert for central Indiana, warning of heavy rain and thunderstorms. "Thunderstorms may be severe with damaging winds and large hail as the main threats," the alert said. "The storms will also produce dangerous lightning and brief heavy rainfall."
The Hoosier Lottery Grandstand at the state fairgrounds, where the concert was scheduled to take place, can seat more than 15,000 people. Underneath the stage are dressing rooms and other facilities.
Last month, a severe storm toppled a stage when classic rock band Cheap Trick was performing. No one was seriously hurt during the incident at the Cisco Ottawa Bluesfest in Canada.
Many famous acts have performed at the Indiana State Fair through the years, including Bruce Springsteen, Kanye West and Garth Brooks. In 1964, the Beatles performed two sold-out shows to an audience of almost 30,000.