AT&T filed a civil suit against MCI this week as an expansion of its claim that MCI is engaging in a shady call-routing scheme.

The carrier’s lawsuit, filed in the U.S. District Court for the Eastern District of Virginia, seeks damages under the federal Racketeering Influenced and Corrupt Organization (RICO) Act. AT&T alleges that MCI illegally routed calls through Canada to avoid paying access fees, a charge initially made in July.

The lawsuit includes claims that MCI is intentionally trying to hurt AT&T by fraudulently requiring the carrier pay access fees directly to MCI.

MCI, still legally known as WorldCom, refutes AT&T’s claims, but says that it is conducting its own investigation to reveal and correct any wrongdoing. MCI has not commented specifically on the lawsuit.

The Department of Justice, FCC, House Energy and Commerce Committee and a mass of lawyers are also investigating AT&T’s claims.

AT&T’s first claims were filed with the federal bankruptcy court in New York that’s handling MCI’s case. AT&T is seeking payback after MCI emerges from bankruptcy.