WASHINGTON (Reuters) - The U.S. Securities and Exchange Commission (SEC) on Tuesday sued Morningstar Credit Ratings LLC for allegedly violating U.S. securities laws in rating commercial mortgage-backed securities, the regulator said in a statement. Morningstar allegedly violated disclosure and internal controls requirements in 30 commercial mortgage-backed securities transactions from 2015 to 2016 when the agency allowed analysts to make undisclosed adjustments to key stresses in its modeling, the SEC said. Counsel for Morningstar could not be reached immediately for comment.