Blow-down test ignites fatal blast at plant

At least 12 people were injured in the explosion at the Kleen Energy Systems plant in Middletown, about 30 kilometres south of Hartford. Crews with dogs are still searching the rubble.

Deputy Fire Marshal Al Santostefano said nobody was believed to be unaccounted for.

The 620-megawatt plant is being built to produce energy primarily using natural gas. Santostefano said workers for the construction company, O&G Industries, were purging the gas lines, a procedure he called a "blow-down," when the explosion occurred.

Officials had not released the conditions of the injured but said some were considered very serious.

A spokesman with the U.S. Chemical Safety Board said the agency is mobilizing an investigation team from Colorado and should have the workers on the scene already.