NEW HAVEN, Conn. — A federal agency investigating a power plant explosion in Connecticut that killed six workers last month says some workers were putting in long hours and they're looking into whether fatigue played a role.

Authorities say the Feb. 7 explosion at the Kleen Energy Systems plant in Middletown happened as workers were using natural gas to clean out gas lines.

U.S. Chemical Safety Board lead investigator Donald Homstrom says some workers were working 12-hour shifts, including some of those involved in cleaning the gas lines.

Kleen Energy declined to comment.

Erik Dobratz, whose father Ray Dobratz was killed in the blast, said last month his father had told him he was working 12 hours a day, seven days a week, for six months.

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