Samples taken from animals at the farm at Cushendall have tested positive for the virus.
A three kilometre exclusion zone has been put in place around the farm. A cull of animals in the area is under way.
Cushendall is in the Glens of Antrim, an area well known for hill farming.
It is thought thousands of sheep will now have to be culled in the area as attempts continue to contain the disease.
'Airborne'
Department of Agriculture officials are trying to establish how the disease got onto the farm.
In a statement on Sunday, Agriculture Minister Brid Rodgers said: "The source of the outbreak has not yet been established so I want to appeal to all farmers in County Antrim to ensure that absolutely no livestock movements take place."
Some farmers in the area are fearful that the airborne virus could have travelled across the Irish Sea from south-west Scotland, which has had severe problems with foot-and-mouth.
Cushendall is about 50 miles from the second outbreak at Ardboe, County Tyrone.
More than 4,000 animals are being slaughtered in the vicinity of the Tyrone farm where the disease was confirmed on Friday.
The only other case was confirmed on 1 March on a farm at Meigh in south Armagh, nearly 50 miles from Ardboe.
The disease has now spread through three counties, affecting the north east, south east and the middle of the province.
'Huge setback'
The Ardboe case has already led to the reimposition of the European ban on meat and dairy exports from Northern Ireland.
Speaking on Saturday, Brid Rodgers said the Ardboe outbreak was a huge setback for the whole agricultural industry.
"It comes just at a time when our hopes were high that we might have escaped this dreadful scourge," she said on Saturday.
Mrs Rodgers said all pigs within a three kilometre zone and all sheep and cattle in a one kilometre zone of the County Tyrone farm would be slaughtered.
Meanwhile, it has been confirmed that the army is to help with the disposal of animal carcasses. The move follows a request from Northern Ireland's first and deputy first ministers.
A statement from the Northern Ireland Office on Saturday night said: "The Secretary of State for Northern Ireland, Dr John Reid MP, in consultation with the Secretary of State for Defence, the Rt Hon Geoff Hoon MP, has agreed that the army will provide support to DARD in the disposal of animal carcasses."
Services affected
The outbreak in Ardboe has affected Easter Sunday church services.
Presbyterian minister, the Reverend Robert Buick moved his Easter service from Ardboe to Stewartstown because of fears of spreading the disease.
He said some of his congregation were reduced to tears by the situation.
Catholic Primate Dr Sean Brady said Easter services in the infected area could ahead.
But he warned that "if anybody feels they are a source of risk they should not travel to church services".
'Family horrified'
The daughter of Paddy Donnelly, the farmer at the centre of the Ardboe outbreak, said the family were distraught.
Eileen Donnelly said they were horrified about the consequences for neighbouring farms.
"We are a very close knit community, we'll just have to get through this and pick up the pieces afterwards," she said.
An emergency meeting of the Northern Ireland Executive is being held on Monday to discuss the crisis.
Meanwhile, vets from the Department of Agriculture have said they are mystified as to how the virus got to the Arboe area.
They are appealing for information which could help them trace the source of the infection.
The Department of Agriculture can be contacted on its helpline numbers on 02890 524279 or 02890 524590 between 0830 - 2100 GMT.