Six workers at the Hanford Nuclear Reservation are receiving medical evaluations after they reported smelling chemical vapors at two underground storage tank farms.

Washington River Protection Solutions, which operates the underground tanks at Hanford, says five of the workers reported symptoms typically related to chemical vapor exposure.

The employees were working in or near Hanford's AP and SY Tank Farms when the vapors were reported. All workers immediately exited the area and moved upwind.

Hanford officials are taking samples and checking for possible sources of the vapors.

There have been numerous incidents in recent months when Hanford workers have reported smelling chemical vapors while working in the tank farms.

The tanks contain radioactive wastes left over from the production of plutonium for nuclear weapons.