RICHLAND, Wash. -- A worker at the Hanford Nuclear Reservation in Washington state got radioactive contamination on his clothing this week during an incident at an underground waste storage tank that indicated a possible leak.

Contractor Washington River Protection Solutions said the worker was removing a robotic device out of the space between the double walls of Tank AZ-101 on Thursday evening. Monitors detected radiation at three times the expected level, and the workers left the area, said the company, which operates the storage tanks for the U.S. Department of Energy.

Radioactive contamination was found on one worker's protective clothing, which was removed, the company said. Monitors showed no further contamination on that worker, and all members of the crew were cleared to return to normal duty, the contractor said.

Hanford is near Richland, Washington, and for decades made plutonium for nuclear weapons. Millions of gallons of the most dangerous wastes produced by that work are stored in 177 underground tanks, many of which are decades old and have leaked.

This incident came after last week's accident in which the roof of a tunnel that contains nuclear waste partially collapsed at Hanford, prompting the evacuation of nearby workers. No one was injured in that event, and Hanford officials said no airborne release of radiation occurred.

But Washington Gov. Jay Inslee said Friday he was alarmed by the two incidents.

"It is another urgent reminder that Congress needs to act, and they need to act quickly," Inslee said. "We expect the U.S. Department of Energy to immediately investigate and report on the source of contamination."

Washington Attorney General Bob Ferguson said the latest incident strengthens his resolve to force the Department of Energy to finish the cleanup of the sprawling site. That cleanup is forecast to last until 2060 and cost an additional $100 billion.

"The risks at Hanford to workers and the environment are all too real, and today's news is just another illustration of how tenuous the situation is," Ferguson said Friday. "This isn't the first potential leak, and it won't be the last."