WORKERS at a nuclear plant in the US have been told to "take cover immediately" following an incident involving plutonium and uranium tunnels.

A text message alert was sent to workers at the Hanford plant in Washington around 6am local time today - or around 2pm in the UK.

5 The B Reactor at Hanford, near Richland, Washington Credit: Alamy

The message read: "WTP Alert: The WTP Site is in Take Cover. Go to the closest Take Cover facility now. Avoid eating or drinking until further notice.

"Await further instructions."

NBC reported the warning was issued as a precaution to workers in the 200 East Area of Hanford after steam was observed coming from Plutonium/Uranium Extraction Facility (PUREX) Tunnel 2 during a tunnel filling operations.

There was no indication of a release of hazardous material.

5 One of the double-shell tank farms containing six underground tanks Credit: Getty Images - Getty

5 The entry sign at the United States Department of Energy, Hanford Site Credit: Alamy

5 Construction work continues at the Hanford Nuclear Reservation June 30, 2005 Credit: Getty Images - Getty

5 Hanford Vit Plant media relations contact says he can confirm a "Take Cover" alert went out to employees on Friday morning Credit: NBC

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According to the Hanford government website the main function of the facilities in the 200 Area is to remove plutonium from uranium fuel rods after they had been subjected to the nuclear chain reaction.

The Department of Ecology website states that in May 2017, a portion of the roof of PUREX Storage Tunnel 1 on the Hanford site collapsed.

The government department's website read: "We issued an order to the U.S. Department of Energy to ensure that Tunnel 1 and Tunnel 2 are stabilized to minimize the danger of further collapses resulting in the release of radioactive contaminants."

Hanford nuclear plant is a 586 square mile site that's a city in itself and which helped to usher in the atomic age