Since Dec. 8, six workers at the Hanford Site have shown up as possibly contaminated. One worker was possibly contaminated twice.

It happened at the Plutonium Finishing Plant — a massive building that used to make so-called plutonium buttons for bombs since 1949.

The workers wear small lapel meters on their collars. Those gave the signals that there might have been elevated levels of radioactive material around them.

The workers now have to undergo a bioassay. They test each worker’s feces to see if they might have ingested some radioactive material.

The contractor doing the work for the federal government said they will only restart work when the possible contamination events have been sorted out.

Watch: The Waste That Remains At Hanford