ATF: Intentional fire caused fatal blast at Texas plant

DALLAS (AP) — A fire that was intentionally set caused the 2013 explosion at a Texas fertilizer plant that killed 15 people, federal officials said Wednesday, describing the blaze as "a criminal act."

The fire caused ammonium nitrate to ignite, triggering a massive explosion that also injured hundreds of people and left part of the small town of West in ruins.

The ATF also released a statement saying investigators determined the fire was "intentionally set" after investigators conducted more than 400 interviews, a fire-scene examination, reviewed witness photos and videos, and conducted "extensive scientific testing" at an ATF fire research laboratory.

Federal regulators determined that factors contributing to the deadly explosion included careless storage of potentially explosive materials and lack of ventilation, along with inadequate emergency response coordination and training, such as hazardous materials training.

The Chemical Safety Board's report, which the panel approved in January, noted that Texas had 80 plants that stored more than 5 tons of ammonium nitrate, a chemical used in fertilizer, and that 19 plants storing fertilizer-grade ammonium nitrate operated within a half-mile of a school, hospital or nursing home.