COEUR d'ALENE - Coeur d'Alene firefighters knocked down a small brush fire on Tubbs Hill Thursday morning, but the cause of the fire is still under investigation.

Coeur d'Alene police responded to the fire first after a column of smoke was spotted near the top of the mountain just before noon. Coeur d'Alene firefighters arrived shortly afterward and began digging fire lines around the blaze.

Idaho Department of Lands fire investigators were called to help determine the cause of the fire, which torched about one-tenth of an acre on the southwest side of Tubbs Hill.

"Whenever we have a wildland fire, we call them in for assistance," said Deputy Fire Chief Glenn Lauper.

Lauper said a fire investigator can get on the ground and look at how the grasses burn and other clues to determine where it started.

He said when the fire is moving, the grass burns in a cupping fashion, showing the direction and path of the fire. When the ground is burnt in an area where all the grass is pointing in different directions, Lauper said, that is usually where the fire started.

Shane O'Shea, assistant fire warden for IDL, spent a little more than an hour determining the origin of the fire, but he said more must be done to determine the cause.

"There are nine causes that we look for and we have to eliminate eight of those to determine the cause," O'Shea said. "We have three of them that we can't eliminate yet."

The three potential causes that cannot be readily eliminated are children, smoking or another incendiary device, O'Shea said.

"Considering the time of day, I think children causing the fire is highly unlikely," he said.

Sgt. Brett Walton said the police department will consider the fire under investigation.