By Laura Zuckerman
SALMON, Idaho (Reuters) - An evacuation order was lifted on Friday for hundreds of workers at a U.S. Energy Department nuclear site in Idaho as firefighters battled for a second day to tame a wildfire that has scorched 30,000 acres of the sprawling compound.
The blaze at the Idaho National Laboratory, an 890-square-mile complex with three active reactors in the high desert of eastern Idaho, presents "no known radiological hazard to the public at this time," lab officials said in a statement.
As the fire grew in size and intensity, the lab on Thursday evening had ordered nonessential personnel to leave a key facility called the Materials and Fuels Complex, where spent nuclear fuel and radioactive wastes are processed. The facility normally is staffed by about 800 workers during the day.
At the same time, workers at another lab installation, the Idaho Nuclear Technology and Engineering Center -- where spent radioactive fuel rods are cooled in storage ponds -- were told to take shelter inside that facility because of heavy smoke, said lab spokeswoman Misty Benjamin.
The evacuation and sheltering orders were lifted Friday morning. No special precautions were known to have been taken so far in surrounding populated areas, including Idaho Falls, a city of roughly 57,000 people about 15 miles east of the lab.
The cause of the fire, battled by 50 firefighters from the lab whom the U.S. Bureau of Land management equipped with bulldozers and aircraft, is under investigation.
It is the second of two blazes that have broken out at the lab this week amid soaring temperatures, gusting winds and lightning strikes.
Crews on Monday contained a blaze that burned more than 100 acres of sagebrush and parched grasslands on the northwest edge of the site. Fire managers said that fire was sparked by a vehicle with a blown tire dragging its metal rim along the pavement of a state highway.
The blaze, which blackened about 28,000 acres of lab property on Thursday, had grown to between 30,000 and 35,000 acres as of Friday morning, lab officials said.
Some 6,000 employees and contractors work at the Idaho National Laboratory, the Department of Energy's lead facility for nuclear reactor technology.
The installation last year grappled with the largest fire in its history, a conflagration that charred 109,000 acres. That fire brought down power lines at the Materials and Fuels Complex, causing officials to rely on backup generators.
Two large-scale fires at the facility within one year sparked alarm among activists with the Snake River Alliance, Idaho's nuclear watchdog group.
"These fires underscore how the nuclear industry and practices at Department of Energy sites pose threats because of unexpected events like floods, fires, earthquakes or other natural disasters," said Liz Woodruff, executive director of the Snake River Alliance.
The blaze at the lab was among five that erupted Thursday in eastern Idaho amid hot and windy conditions that led the National Weather Service to elevate the fire risk for much of the interior West.
Fires have charred tens of thousands of acres across Idaho and the Northern Rockies in recent days, including parts of Montana, Yellowstone National Park and northwestern Wyoming.
(Editing by Steve Gorman and Jerry Norton)