Alabama's agriculture chief has quarantined 10 containers carrying used farm tractors from Britain, saying they need to be tested for foot-and-mouth disease.
The containers will be tested in an effort to prevent the disease from entering the United States, Alabama Agriculture and Industries Commissioner Charles Bishop said.
State Agriculture Department spokesman Ralph Holmes said officials are concerned the virus could be on tractor parts and added: "That virus could be in the mud on the tractor wheels."
Docks officials did not have immediate access to the ship's manifest to determine details on the shipments, including how many tractors there were.
The containers have been unloaded but not opened, they said.
Alabama Farmers' Federation spokesman Paul Till applauded Mr Bishop's move, saying the cattle industry could suffer greatly if the virus invaded the state's cattle population.
"We've not had that disease in the United States since the 1930s," he said.
Sarah Teague, spokeswoman for the state docks, said that if any evidence of the disease was found, the tractors could remain in the country after being disinfected.
PA