HARRISBURG — An offer of $500 in free slot-machine playing credits was accidentally mailed to 55,000 gambling customers, leaving a Pennsylvania casino scrambling to placate customers and figure out how the mistake happened.

Hollywood Casino at Penn National Race Course decided Monday to partially honor the offer after frantically calling tens of thousands of customers over the weekend.

The mistake was reported by a television station, which said some confused and angry customers began trying to take advantage of the offer that took effect Monday.

FAIRMONT, W.Va. — Allegheny Energy said it bought land near Fairmont for its new multistate transmission operations headquarters.The Pennsylvania-based utility announced in August it planned to build the headquarters in the Interstate 79 High Technology Park.On Monday, Allegheny Energy said it bought 9.5 acres and selected an engineering and architectural firm to begin working on the building's design.The utility said it still plans to begin construction next year, and hopes to open the center by 2011.