BEND, Ore. (AP) — Diminished air quality has returned to much Oregon because of wildfire smoke, reaching unhealthy levels in the central and southern parts of the state.

The Oregon Department of Environmental Quality on Thursday expanded and extended an air quality advisory due to smoke from California and Oregon wildfires.

The updated advisory covers central, south-central and southwest Oregon, as well as Harney County, through noon Saturday, The Oregonian/OregonLive reported.

Cities including Ashland, Bend, Klamath Falls and Medford had unhealthy air quality early Thursday afternoon.

Other areas, including Burns, had air that was unhealthy for sensitive groups. And a wide swath of the state had moderate air quality.

Portland and Salem had good air quality.

The advisory said smoke likely would be thickest during nights and mornings.