A leading horse food producer has advised customers not to feed its products to animals as it investigates the presence of a banned substance in some of its products.

GAIN Equine Nutrition said that Zilpaterol, a synthetic beta-agonist approved for use as a performance-enhancer in some beef production systems outside of the EU, has been found in some of its equine feed range.

The contaminants were found in products in France, as a result feed products in Ireland and the UK have also been tested.

GAIN Equine has insisted that the synthetic substance has never formed part of any formulation in any of its animal nutrition ranges.

The company said that as soon as it became aware of the issue its quality and control team immediately commenced testing feed products and retained samples.

In a statement this evening it says it is working closely with all appropriate agencies, including the Irish Department of Agriculture, to fully investigate the source of the contamination.

Martin Ryan, Head of GAIN Equine said: "We apologise sincerely to our valued customers for the inconvenience caused by this incident and we are committed to promptly keeping you fully informed.

"A thorough investigation and trace back of all feed ingredient sources is under way as a matter of urgency to determine how this external contaminant could have found its way into some batches of our equine product."