OKLAHOMA CITY (AP) - The U.S. Department of Justice has opened an investigation into possible antitrust violations by Chesapeake Energy Corp.
    The Journal Record reports  the agency has subpoenaed documents related to how the driller pays royalty owners and accounts for oil and gas reserves.
    Chesapeake disclosed the subpoena Thursday in a regulatory filing with the U.S. Securities and Exchange Commission. University of Central Oklahoma economics professor Jeremy Oller, an expert witness on antitrust legal matters, says the Justice Department is likely examining other oil and gas companies as part of the investigation.
    The filing says the Justice Department and other agencies have asked Chesapeake for documents, testimony and information related to the company's oil and gas leases and purchases. The company also received subpoenas from the U.S. Postal Service and state agencies.