A Utah State Prison inmate arrested in Yellowstone National Park in connection with the rape of a female firefighter has been indicted by a federal grand jury in Cheyenne.

The U.S. Attorney's office in Cheyenne said Roger Lopez, 33, of Lay-ton, Utah, was indicted Friday and made an initial appearance in U.S. District Court in Cheyenne on Tuesday.The indictment says that Lopez caused a woman to engage in a sexual act through the use of force.

Lopez, a member of the prison's Flame-N-Go firefighting unit, was arrested last week in connection with the rape at knifepoint of a 20-year-old firefighter.

After the arrest, the 20-man prison unit was pulled out of the park and returned to Utah.

The unit is comprised of minimum security inmates on a work-release program. Lopez joined the firefighting unit in May.