San Francisco, Aug 26 (IANS): A 35-acre wildfire burning near a reservoir in the Bull Run Watershed in Clackamas County, US state of Oregon, threatened Portland's drinking water.

The tap waters in the city remained safe to drink so far, officials said on Friday as quoted by Xinhua news agency report.

The Bull Run Watershed long has been closed to visitors to protect the water source, which has been called "Portland's enduring jewel".

The Camp Creek Fire is burning south of Reservoir 1, about three miles from the city's Headwaters treatment facility, according to US Forest Service Spokesperson Heather Ibsen.

The wildfire was sparked by lightning overnight and first reported before dawn on Friday. The blaze is considered zero per cent contained, she added.

More than 200 miles away, the lightning strikes in Oregon overnight sparked at least six fires in the Willamette National Forest, according to the Eugene Interagency Coordination Centre.

Meanwhile, evacuations have been upgraded for residents threatened by the Smith River Complex fire burning on the border of Oregon and California states.