Controls have been lifted at a Merthyr Tydfil meat processing plant, after it was linked to a Surrey farm where foot-and-mouth disease was found.
On Monday a third farm in Surrey was found to have foot-and-mouth
There were no signs of the disease at St Merryn Meat at Dowlais, which employs 1,000 workers.
The Welsh Assembly Government has stressed the investigation, which began on Tuesday, was part of a routine tracing exercise.
The company said it was now fully operational.
Liveestock was being received from Wednesday evening, for processing on Thursday.
On Monday night a third farm in Surrey was found to have foot-and-mouth in the latest outbreak of the disease.
Officials discovered cattle had been sent from the farm to St Merryn meat about a week ago, before movements across Britain were banned.
The cattle had been routinely inspected by vets on arrival at the plant, and after slaughter, and no sign of disease was found.
But on Tuesday production at the plant was halted as the link was established.
Livestock lorries were turned back as the investigation got underway.