Comerica Inc., a Dallas-based bank that has helped finance U.S. shale drillers, fell the most in three years after reporting Friday that it set aside more money to cover souring energy loans. Shares fell by as much as 6.8 percent, the most since October 2011, after the bank said Friday that its at-risk energy loans grew by $329 million in the second quarter, with past-due accounts up by $100 million. About 14 percent, or $578 million, of the bank’s energy portfolio has been classified as “criticized,” the bank said in a call with investors and analysts. Banks that have been critical to the U.S. shale boom have set aside more cash to cover potential losses after oil fell 51 percent in the past year to about $50 a barrel. This week, JPMorgan Chase & Co., Wells Fargo & Co., Bank of America Corp. and Citigroup Inc. all reported increased […]