The men - who worked at the plant - were hunting ducks on their day off

A pair of duck hunters triggered a security alert at a nuclear weapons assembly plant in Amarillo, Texas.

Officials put the plant into lockdown after getting reports of individuals in camouflage gear stalking across the road from the factory.

They turned out to be two plant employees who had decided to spend their day off hunting fowl.

The plant was briefly shut as a "precautionary measure", a plant official said.

"They were just doing what people do around here," said Carson County Sheriff Tam Terry.

"They just had a lot more company than they were planning on."

The pair, who sparked the alert when spotted early in the morning carrying arms and dressed in camouflage gear, were later found in a nearby field setting up goose decoys.

No charges will be filed against the men who both had permission to hunt from the local landowner.