A fiery encore to the Magna municipal fireworks display Friday that burned 50 acres and caused $250,000 in damage was technically the fault of the company staging the show although the firm was not negligent, according to results of a Unified Fire Authority investigation.

UFA spokesman Ben Sharer said investigators found "hundreds" of spent fireworks casings in the field, owned by the Kennecott Co., across from Magna Park, near 8400 West and state Route 201. Sharer said that although the blaze appears to have been caused by the casings, which were apparently carried into the field by high, upper-level winds on Friday night, there is no cause to believe the display company was negligent.

The company was issued a permit for the show after passing a UFA inspection and providing proof of a $1 million liability insurance policy. Sharer said UFA fire inspectors found the company's safety preparations prior to the show had "exceeded regulations."

The fire was brought under control by UFA firefighters, with help from Rocky Mountain Raceway, Kennecott employees and nearby residents. Sharer said the lack of water access in the area required fire crews to utilize water-tender trucks to battle the blaze. Equipment was brought in by both the raceway and Kennecott to aid UFA crews.

No homes or large structures were threatened by the blaze, though a small shed and multiple power poles, all Kennecott-owned, were consumed by the fire.