ELLENSBURG, Wash. -

 A wildfire that burned sagebrush and grass south of Ellensburg in central Washington was about 80 percent contained by Friday morning.

Debbie Robinson at the state Department of Natural Resources say the blaze held overnight to about 4,000 acres, or six square miles. It was reported Thursday night.

Robinson says there were lightning strikes in the area recently, but the cause of the fire is under investigation. No homes are threatened.

Crews of about 90 people planned to work Friday to verify the perimeter of the blaze, improve lines around it and tackle hotspots.

A section of eastbound Interstate 82 was closed for about three hours Thursday night due to the smoky fire in the Manastash Ridge area. It reopened when the fire was no longer close to the roadway.