The Margo Fire burned through thick vegetation in the San Pedro River bottom near Dudleyville in Pinal County on Thursday continued to be estimated at 500 acres with containment around 20% of its perimeter as of Friday, officials said.

Cause of the fire near the unincorporated Pinal County town was under investigation.

The county Sheriff’s Office said approximately 200 residents were evacuated and that the evacuation notice might be lifted Friday evening or Saturday morning.