Contractors are building a road to a collapsed train tunnel site at the Hanford nuclear reservation in southeast Washington state. Their goal is to keep any radioactive contamination from escaping the hole that was found Tuesday.

 Workers have most of the road in place to get heavy equipment to the collapsed tunnels site. Mark Heeter with the U.S. Department of Energy said contractors will be using around 50 loads of clean fill dirt from a large dump site at Hanford to cover up the hole.

Thousands of workers were sent home after a portion of underground train tunnel collapsed Tuesday morning. Workers and investigators scrambled to study the problem and lock things up. Federal Department of Energy officials said no one was hurt and no contamination has spread out of the tunnel area.

The collapse is near PUREX, an old Cold War factory in the center of Hanford that was used to extract plutonium for use in nuclear bombs. The railways moved irradiated rods into the building for that extraction process and sent contaminated equipment away from the building shielded underground.

The tunnels were constructed of wood and concrete and are covered with soil about eight feet deep.