A pyrotechnics worker from Moorpark died Monday from severe burns suffered when an Independence Day fireworks display blew up prematurely in a suburb of Phoenix.
Federal investigators are searching for the cause of a blast hours before the start of the show at the Peoria Sports Complex that killed Michelle Galanda, 36.
Galanda was burned over 90% of her body and died at the Maricopa County Medical Center.
Four other employees of Salt Lake City-based Lantis Fireworks & Lasers were injured.
Jeff Fraizer, 36, also of Moorpark, was hospitalized in critical condition with burns on 60% of his body. Joyce Gyorwfy, 59, of Newbury Park, was in fair condition with burns. The other two employees were treated and released.
Stacks of fireworks started detonating as employees were unloading them at the complex, the spring-training home of the Seattle Mariners and San Diego Padres.
Lantis workers had dug several trenches and set up a big steel tube to hold the fireworks once they were hooked up to a control board, said Larry Bettendorf, a spokesman for the U.S. Bureau of Alcohol, Tobacco and Firearms.
"We believe they were working on the fireworks. The fireworks may have gone off right at their feet," he said.
A witness said he heard "50 to 60 explosions."
"I saw tons of white smoke filling up the baseball field and fireworks exploding along the ground. It sounded like the grand finale of a fireworks show," said Chris Powell, who was setting up his camera across the street to photograph the display.
Company officials didn't immediately return calls to the Associated Press on Monday.
Lantis, which staged Peoria's Independence Day fireworks show last year, had planned to explode more than a thousand shells, Peoria fire spokesman Mike Tellef said. The show, expected to draw about 20,000, was canceled.
ATF bomb crews swept the fields Monday for unexploded fireworks. Bettendorf said many things could have caused the explosion, including static electricity, a spark or electrical malfunction.
Bettendorf said it was unlikely that the 100-degree heat contributed to the explosion, although the high temperature could have made the explosives more unstable.