Aug 25 (Reuters) - U.S. authorities are investigating German lender Deutsche Bank"s (DBKGn.DE) asset management arm DWS Group (DWSG.DE) after the firm"s former head of sustainability said it overstated how much it used sustainable investing criteria to manage its assets, the Wall Street Journal reported on Wednesday. The probes, by the U.S. Securities and Exchange Commission (SEC) and federal prosecutors in Brooklyn, New York, are in early stages, the newspaper said, citing sources. A DWS spokesperson told Reuters the firm does not comment on litigation or regulatory matters. Deutsche Bank and a spokesperson for the U.S. Department of Justice declined to comment on the WSJ report, while an SEC spokesperson said: "The SEC does not comment on the existence or nonexistence of a possible investigation." The SEC, the top U.S. markets regulator, earlier this year established a task force to root out misconduct related to environmental, social and governance (ESG) issues. With a record $51 billion flooding into sustainable U.S. funds in 2020 alone, according to Morningstar, investors need to be better informed, the SEC has said. read more Deutsche Bank has been trying to restore its image in Washington amid several investigations into its dealings with U.S. President Donald Trump, a longtime client. In January, the firm agreed to pay nearly $125 million to avoid U.S. prosecution on charges it engaged in foreign bribery schemes and manipulated precious metals markets, the latest blow for the bank as it tries to rebound from a series of scandals. read more