The Oregon State Police have launched an investigation into an incident Sunday when a female trooper used a TASER on a naked, 11-year-old girl to stop her from crossing Interstate 5.

Motorists spotted the girl, later identified as husky and suffereing from autism, attempting to cross the highway at 4 a.m. Sunday. When the trooper arrived, he was "worried about hallucinogenic impairment," an agency spokesman told the Oregonian.

After two warnings, the trooper took the girl down with a TASER. The child's father said the use of force was excessive.

The girl's behavior and physical development led medical staff and the trooper to think she was in her late teens to early 20s, according to an agency statement.