Washington (CNN) -- Two U.S. marshals were burned Monday morning when a rape suspect they were attempting to arrest evidently doused himself with a flammable liquid and set himself on fire, a spokesman for the U.S. Marshals Service said.

The marshals, one male and one female, were attempting to serve a bench warrant to a rape suspect around 8 a.m. at an apartment in the basement of a Washington residence when the man lit himself on fire, Deputy Marshal Cole Barnhart told CNN.

"Details are still very unclear," Barnhart said. "We don't know how the female deputy got burned, but she was on fire (and) another deputy went to her aid," suffering burns in the process.

"We just know that the female deputy received more severe burns" than her colleague, he said. "How she got those, we don't know yet." The female marshal was conscious when she arrived at the hospital, he said.

The suspect, described as a 20-year-old male, was severely burned "over a good portion of his body," Barnhart said. All three burn victims were transported to a hospital, authorities said. Barnhart declined to name any of the individuals pending notification of their families.