By Ahmed Aboulenein and Manas Mishra WASHINGTON (Reuters) -Lawmakers grilled U.S. Food and Drug Administration officials on Wednesday over what they saw as a lack of urgency in the agency’s response to complaints about possible baby formula contamination at a now shuttered Abbott Laboratories plant that led to severe nationwide shortages. FDA leaders appeared before a congressional panel to answer questions about the crisis after Abbott in February recalled some products and closed its manufacturing plant in Sturgis, Michigan. “There are also questions surrounding the timeline of FDA’s investi…