A series of wildfires burned out of control late Friday along a major highway in western Montana (search), prompting authorities to establish roadblocks to keep motorists from getting caught in the billowing smoke.

Flames along Interstate 90 burned right to the edge of the town of Alberton (search) and sometimes into yards. One building was destroyed.

A 90-mile span of the highway had been closed Thursday from just west of Missoula (search) to St. Regis, just east of the Montana-Idaho border. The eastbound lanes were reopened late Friday.

Officials credited quick action by fire crews with saving dozens of houses in this community of 400 people about 28 miles west of Missoula.

Sharon Sweeney, a spokeswoman with the Lolo National Forest, said firefighters were able to save all but the one building, a shop containing vintage cars, tools and antiques.

Outside town, firefighters were digging a line to protect about 10 houses that were still threatened near West Mountain, which was aflame on both its east and west flanks.

State officials closed 20 miles of the Clark Fork River to public use because helicopters with 500-gallon buckets were scooping water from the river to help fight the fires.

Authorities were investigating what started the flames, but said arson or possibly a vehicle dragging something that emitted sparks were both possible causes.

"This absolutely wasn't an act of God," said fire spokesman Scott Waldron.

Also in Montana, a fire in the Bitterroot Valley south of Missoula expanded Friday to at least 1,400 acres. The blaze was being allowed to burn, but firefighters may have to be assigned if it moves out of the wilderness into nearby public forest lands.

Large fires also were active Friday in Alaska, California, Colorado, Hawaii, Idaho, Nevada, Oregon, Texas, Utah and Washington, the National Interagency Fire Center reported. So far this year, wildfires have charred 4.9 million acres, compared with 5.5 million at the same time last year, the center said.