The FBI believes a 14-year-old girl missing from Erie, Pa., is traveling with a Billings man who was charged with raping five girls in Fergus County in 2005.

Sierra Lillie was reported missing Sunday evening and officials believe she is with 21-year-old Donald Cates, with whom she had been communicating via e-mail and telephone for the past two years.

Sierra's mother said her daughter believed Cates was a teen.

In 2005, Cates, then 17, was charged with raping five girls. A mistrial was declared because a police officer interrogated him without notifying his parents.

A recent Montana Supreme Court decision said it would not constitute double jeopardy to re-try Cates on the rape charges.