A superintendent of an Indiana school district, where a stage collapse injured 16 high school students, said Friday the section that gave way was only a few years old, but it was not clear whether it was ever subject to inspection.

The concerns surrounding the regulation of the orchestra pit cover that collapsed during Thursday night’s musical at Westfield High School is reminiscent of questions that arose in 2011 when winds toppled a state rigging onto fans awaiting a performance by Sugarland at the Indiana State Fair.

Seven people were killed and dozens were injured in the collapse, which sparked new state rules on temporary, outdoor state rigging equipment. Thursday’s collapse was not deadly and all of the students who were injured were out of the hospital by Friday afternoon.

John Erickson, a spokesman for the state’s Department of Homeland Security, said the state rules adopted after the fair rigging collapse do not apply to the type of indoor stages found in schools. He said it was unclear whether inspections of public school stages are required under any state rules.

"It does not look like plans were required to be filed" for the stage at the school, Erickson said.

Westfield Washington Schools Superintendent Mark Keen said he wasn't sure who, if anyone, handles inspections of the district's school stages. He said school officials are delving into records and will provide information to investigators.

The stage collapsed Thursday night as clapping and singing students performed Journey’s “Don’t Stop Believin” in the finale of a concert called “American Pie.” Video shows students plummeting out of sight before the music cuts off and screams are heard.

Westfield police Capt. Charles Hollowell said Friday that the injured students only suffered minor injuries and were “doing really well.” One student who was thought to have suffered a serious injury was fine and was the last student released from the hospital.

The auditorium remained closed Friday except to investigators.

 The State Fire Marshal's office, Indiana State Police and Indiana's workplace-safety agency were investigating. Indiana Gov. Mike Pence said in a statement that they would "make every effort to prevent this or worse from happening in the future."

Keen said the school often rents its auditorium to outside groups and the facility gets heavy use. He said the orchestra pit cover, which is used during some productions to get the performers closer to the audience, was replaced a few years ago after the original 1997 cover was damaged.

He said officials were checking records to determine whether it had ever been inspected.

"I know we have records when they come in and inspect our football bleachers and when they inspect the gymnasium bleachers and so we're trying to find if there are inspection reports on (the pit cover) as well," Keen said.

J.T. Coopman, executive director of the Indiana Association of Public School Superintendents, said he expected the accident to "jolt people into action" at schools statewide to review the safety of stages.

"That would be the direction that I would be giving my maintenance staff: 'Do we have a structure like this? How often do we inspect it? Are we sure that it's absolutely safe before we use it?'" he said.

The Associated Press contributed to this report