A Connecticut fire official says about five people are unaccounted for after a deadly explosion at an under-construction power plant.

Middletown Deputy Fire Marshal Al Santostefano says it remains unclear whether the workers who are unaccounted for are missing or haven't been contacted yet by authorities.

Santostefano said Monday that 95 percent of the nearly 100 workers who were at the plant are accounted for, judging by conversations with contractors and labor union officials. But he says a section of the Kleen Energy Systems plant remains too unstable to see whether anyone is still trapped.

Authorities say different contractors were working at the site, making it difficult to determine how many people were there during the blast.

Sunday's explosion at the nearly completed plant in Middletown, about 20 miles south of Hartford, killed at least five people and injured a dozen or more. Officials say it happened as workers were clearing a gas line of air.

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