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

Randy Bradbury, a spokesman for the Washington state Department of Ecology, said officials detected no release of radiation and no workers were injured.

He said there were no workers inside the tunnel when it collapsed Tuesday morning but that nearby workers were told to evacuate the area and others who were further away were told to remain indoors.

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Emergency personnel standing by at Hanford.

9:23 AM - 9 May 2017

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A source said crews doing road work nearby may have created enough vibration to cause the collapse.

A message was sent to all personnel telling them to "secure ventilation in your building" and "refrain from eating or drinking."

For decades Hanford made plutonium for nuclear weapons, including for the bomb dropped on Nagasaki, Japan.

It is now the largest repository of radioactive waste in the United States.

Hanford has about 211 million litres of waste stored in underground tanks. Some tanks date back to World War II and are leaking.

The sprawling Hanford site is about half the size of Rhode Island.