NEW HAVEN - (AP) - A federal agency investigating a powerplant explosion in Connecticut that killed six workers last monthsays some workers were putting in long hours and they're lookinginto whether fatigue played a role.

Authorities say the Feb. 7 explosion at the Kleen Energy Systemsplant in Middletown happened as workers were using natural gas toclean out gas lines.

U.S. Chemical Safety Board lead investigator Donald Homstromsays some workers were working 12-hour shifts, including some ofthose 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 aday, seven days a week, for six months.