A 500-acre forest fire is still burning and spreading in the Grapevine area of Pike County. Rangers say it appears to be arson.

The fire is still not contained but crews are working non-stop. Foresters call the fire dangerous and say it appears someone started it this morning on purpose, and then it quickly spread.

Rangers say the fire started small, but spread to several hundred acres in just minutes.

Rangers say they were called about the fire in the Grapevine Mountain area around 8:00 A.M. They say it looks like someone on an ATV set it in several different places, then each fire grew.

The wind is making it hard to contain and is threatening the safety of firefighters.

"It just makes us back off and be careful about where we put our lines in. Kind of look at the big picture a little bit more about the safety of our guys and what precautions we need to take," said Ranger Cody Evans.

The terrain is also causing problems.

"It just wears on the guys. It's just a little bit more physically demanding than a short, smaller fire," added Evans.

No homes are in danger, but rangers recommend ATV riders and others stay away from the mountain while it is burning.

Rangers say if they catch who started this, they will face charges.

Crews hope to contain the Grapevine fire by Friday night. They do not know if the rain will help much.

If you know anything about who set the fire, call the Arson Hotline at 1-800-27-ARSON. You could earn a $1,000 reward if your information leads to a conviction.