An emergency has been declared at the Hanford Nuclear Reservation in southeastern Washington after a portion of a tunnel that contained rail cars full of nuclear waste collapsed.

Hundreds of workers at the site of the tunnel collapse Tuesday morning were evacuated. No workers were in the tunnel. Workers farther away were told to remain indoors.

Randy Bradbury, a spokesman for the Washington state Department of Ecology, said there apparently has been no release of radiation and no workers were injured.

The U.S. Department of Energy Richland Operations Office activated the Hanford Emergency Operations Center at 8:26 a.m. local time, after an alert was declared, according to the official Hanford site.

“There are concerns about subsidence in the soil covering railroad tunnels near a former chemical processing facility,” a statement on the site said. “The tunnels contain contaminated materials.”

A text message sent to all personnel and obtained by KING5 told workers to “secure ventilation in your building” and “refrain from eating or drinking.”

It was unclear if any radioactive materials were released into the air.

Hanford for decades made plutonium for nuclear weapons, and now is engaged in cleaning up the nation’s largest volume of radioactive defense wastes.

The sprawling Hanford site is located near Richland and is half the size of Rhode Island.

(AP)