All foot-and-mouth infected animals in Northern Ireland may not have been traced, Agriculture Minister Bríd Rodgers warned today.
Mrs Rodgers told members of the Northern Ireland Assembly that some 60 livestock may not yet have been accounted for.
The foot-and-mouth outbreak spread to Northern Ireland last month after a consignment of sheep were brought over from Carlisle.
It had been thought that all had been located and destroyed.
But in a statement to the Assembly Mrs Rodgers said there were unconfirmed reports that the batch may have been larger than first thought.
She said: "My staff are presently working with the various police forces to get to the bottom of this, but we are receiving little co-operation from those who are under suspicion, which makes the task much more difficult.
"Until our inquiries into this new information are complete, I am unable to state categorically that all potentially infected animals have been traced and accounted for.
"This matter is being pursued with the utmost urgency and I will update members as soon as I can."
Appealing for any information to be passed to her department immediately, she added: "We are talking about possibly 60, but it is impossible to be absolutely certain."
PA