Ireland's Department of Agriculture has confirmed it is investigating an alleged use of the illegal growth hormone Clenbuterol in cattle.
It is understood an animal tested positive during a random sample as part of the National Residue Control Programme.
However, the department has offered assurances there is no risk to public health from meat currently being sold.
A spokesman said: "The Department of Agriculture, Food and the Marine is currently investigating a case of the alleged unauthorised use of Clenbuterol.
"The investigation follows from a positive result for one animal in a random sample taken as part of the National Residue Control Programme.
"The Department has placed all animals on the farm under restriction pending the completion of the investigation.
"The Food Safety Authority of Ireland is fully aware of the case and has concluded that there is no risk to public health from meat that is on the market."
Clenbuterol can be used illegally to increase the leanness and protein content of livestock.
It has long been banned in the EU for growth in food producing animals because of health concerns which can include increased heart rate and muscular tremors.
In 2012, two beef cattle on a farm in Co Monaghan tested positive for the drug during a similar testing programme.
At that time the animals were tested following a fuel laundering investigation.
