Concertgoers and emergency personnel hold up the stage roof and rigging after it collapsed minutes before a concert by Sugarland at the Indiana State Fairgrounds in Indianapolis August 13, 2011. REUTERS/Steve Baker

Police evidence from the tragic Indiana State Fair stage collapse has been reported missing following a recent break-in at a local warehouse.

Seven people were killed and dozens more injured when high winds brought down scaffolding and rigging right before Sugarland were scheduled to perform at the fairgrounds last August.

Affected audience members launched legal action against the country duo, concert promoters and stage builders, accusing them of negligence last November and the case is due to head to trial on April 1, 2014.

But earlier this month, thieves broke into the warehouse where the wreckage is being stored until the next court date, and made off with a key piece of evidence - the pile of steel cables which supported the collapsed structure.

State Police Captain Dave Bursten tells the Washington Post, "They broke in for the purpose of stripping the electrical wiring from the facility (in order to sell it) and then while they were there, criminals being criminals, it was 'Oh, there's something else we can steal.'"

Kenneth J. Allen, an attorney representing a handful of the victims, has been left troubled by the news.

He says, "Certainly it's evidence that's related to this catastrophe and in that regard given the gravity of the harm that was done it's very important."

Law enforcement officials have yet to name any suspects as the thieves "circumvented" the building's security system.

Sugarland's Jennifer Nettles and Kristian Bush have previously refused to accept blame for the tragedy, insisting the incident was a "true accident or Act of God".