Two senators asked the federal government to investigate a data breach on the payment-card processing systems of Home Depot Inc (HD.N) and five U.S. The retailer has yet to say what was stolen, though experts fear the attackers may have gotten away with more than 40 million payment cards, which would exceed the number taken in last year’s unprecedented attack on Target Corp (TGT.N). Home Depot said customers who shopped at its stores as far back as April were exposed, meaning the breach extended for more than four months including the busy summer season.