A Utah prison inmate battling the Yellowstone blazes was taken into custody after a woman said she was raped.

A spokesman for the U.S. attorney's office in Cheyenne, Wyo., said a firefighter with a crew from the Utah State Penitentiary was taken into custody after a 20-year-old woman firefighter said she was raped at knifepoint Tuesday morning.The spokesman said the case will be heard before a grand jury later this week.

All 20 Utah prisoners have been pulled from the fire and returned to prison, park spokeswoman Joan Anzelmo said. The crew was composed of minimum-security prisoners on a work-release program, she said.

Meanwhile, a half-dozen firefighters fighting the Clover-Mist fire in the northeast portion of the park were treated and released at the Mammoth Clinic this week after inhaling sulfuric acid generated by a hot pool, Anzelmo said.