Fire crews have tacked a dramatic blaze that broke out at Washington state's largest oil refinery, sending up towering flames and creating a thick plume of smoke visible for miles.

Workers at the BP Cherry Point refinery near Blaine were evacuated shortly after the fire started at about 2.30pm local time on Friday in a tower on the refinery's south side.

BP spokesman Scott Dean said the fire was put out 90 minutes later.

The Bellingham Herald said about 100 evacuated workers gathered in a car park to watch the flames.

Mr Dean says all employees were safe and accounted for. He could not say what the tower was normally used for or what it contained.

There was no immediate word on the cause of the fire or the extent of damage.

The one-square-mile refinery employs more than 800 people and can process as much as 230,000 barrels of crude oil a day from Alaska.