A consignment of muscle-building drugs has been seized during an investigation into cross-border cattle smuggling.
Tags used in switching the identities of cattle were also found
Officials are believed to be planning to question more than 20 people about the discovery of anabolic steroids at a farm in Mid-Ulster.
The discovery of 100 bottles of the illegal growth promoters was made by police attempting to trace cattle stolen in the west of Ireland to a farm in County Tyrone.
Michael Steele, who heads a special investigation unit set up by the Department of Agriculture in Northern Ireland, said the find was significant.
"They were anabolic steroids, cocktails of what looked to be four or five substances have been identified by the laboratory so far," he said.
"These are significant because each of the components are in small enough quantities that makes them quite difficult individually to identify."
Police on both sides of the border have been working with the Northern Ireland-based veterinary team as well as the special investigation unit of the Department of Agriculture in Dublin.
The investigating teams also found tags used in switching the identities of cattle set to be sold in Northern Ireland.