NEW YORK (Associated Press) -- Federal authorities plan to arrest two former JPMorgan Chase & Co. employees on suspicion that they tried to conceal the size of the investment bank's $6 billion trading loss last year, according to a published report Friday.The New York Times, citing persons briefed on the matter, reported that Javier Martin-Artajo and Julien Grout are expected to be arrested in London in coming days. Martin-Artajo oversaw JPMorgan's trading strategy in London, while Grout recorded the value of the soured investments, the newspaper reported. A federal grand jury voted to indict both on criminal fraud charges, according to the report. Federal investigators have concluded that Martin-Artajo directed Grout to falsify records and conceal more than $400 million in losses from their superiors at the bank, the newspaper reported. The charges against Martin-Artajo and Grout hinge on the cooperation of Bruno Iksil, a trader at JPMorgan in London who placed the large bets that led to the loss, according to the report. Iksil, dubbed the "London Whale," is not a target of the Justice Department or the Securities and Exchange Commission, according to a separate report in The Wall Street Journal. The U.S. attorney's office in New York declined to comment late Friday. A call left with the FBI office in New York was not immediately returned. The trading loss disclosed in 2012 was an embarrassment for the biggest U.S. bank and raised concerns about risk-taking at Wall Street banks four years after the financial crisis.