A Texas prosecutor says volunteer firefighters south of Dallas have been arrested on charges that they sexually assaulted a man at their fire station as part of a "rite of initiation."

An arrest warrant affidavit says five men ranging in age from 19 to 30 were charged with aggravated sexual assault, while a 23-year-old woman was charged with improper visual recording for using a cellphone to videotape the assault.

Neither the Texas Rangers, who are leading the investigation, nor the affidavit, give a motive for the attack. But Ellis County District Attorney Patrick Wilson said it appears to be part of the initiation of a new fire recruit.

The affidavit says that in January the victim was held down as the men used a sausage to sodomize him.