Natrona County fire investigators say they've yet to determine an exact cause of last summer's Sheep Herder Hill Fire.

The fire scorched 15,556 acres atop Casper Mountain between Sept. 9 and Sept. 16 of 2012.

Fire inspector Dave Baker says the Natrona County Fire District is still looking for answers.

"It's still human caused - that has not changed," Baker said. "The problem is that we can't isolate the exact ignition source."

"It could have been anything from a discarded smoking material, it could have been exhaust from ATV or vehicle use in the area or it could have been intentionally set," Baker said.

The Sheep Herder Hill Fire destroyed 37 homes and was fully contained on Sept. 16.