Ford Motor Co. agreed to pay a $1.5-million civil fine and $5 million in donations because of a February explosion that killed six workers at its Dearborn, Mich., manufacturing complex. Ford and the United Auto Workers union also released a report that said an accidental buildup of natural gas caused the boiler explosion at the Rouge complex. Fourteen other workers were injured in the blast. Separately, Ford reported a 7.6% increase in U.S. sales for August, better than the 4% analysts had expected and capping the industry's best month in nearly 13 years. The fine was part of an agreement between the state of Michigan, Ford and the UAW. The $5 million will go for burn care and and related research and a union scholarship fund in memory of those who died. The fine is Michigan's largest ever for a worker-safety violation. Ford's shares fell 94 cents, closing at $50.94 on the NYSE.