U.S. banks are setting aside more money to cover bad loans to energy companies after oil prices plunged over the last year, raising the possibility that deteriorating loans could start to weigh on their earnings, some analysts said. Loan credit quality for U.S. banks has been improving since the financial crisis. In the first quarter, 2.49 percent of loans on banks’ books were delinquent, the lowest level since the fourth quarter of 2007, according to the Federal Reserve, which hasn’t released second quarter data. The rate peaked at 7.4 percent in the first quarter of 2010. Weakness among energy company loans could be a sign that overall credit quality among U.S. banks has little room to improve, analysts said. Executives from both JPMorgan Chase & Co. and Wells Fargo & Co. told investors last week, when posting earnings, that they were increasingly concerned about loans to oil and gas companies. Texas bank Comerica Inc on Friday set aside about three times as much money to cover bad loans as analysts had expected, sending the regional bank’s shares lower by more than 6 percent after the bank reported earnings Friday. Setting aside more money, known as “provisioning,” hurts earnings.