U.S. Chemical Safety Board Chairman Rafael Moure-Eraso said in a letter Tuesday that the Texas state fire marshal and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives blocked access to key witnesses for three weeks after the April 17 explosion, The Dallas Morning News reported Wednesday.
Fifteen people died and more than 200 others were injured in the blast that flattened most of the town of West, Texas, north of Waco.
In the letter sent to Sen. Barbara Boxer, D-Calif., Moure-Eraso asks the chairman of the Senate's Environment and Public Works Committee to help his team gain access to debris and other evidence removed by ATF and the fire marshal.
He writes that the "incident site was massively and irreversibly altered under the direction of ATF personnel, who used cranes, bulldozers and other excavation apparatus in an ultimately unsuccessful quest to find a single ignition source for the original fire."
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