A 10-year old boy has died and his father has been hospitalised after they were overcome by slurry fumes.
The 51-year-old man and his son were spreading slurry on a farm near Dunloy, Co Antrim, when the accident occurred.
Emergency services attending the scene were unable to save the boy. His father is said to be fighting for his life in the Royal Victoria Hospital in Belfast.
Ballymoney mayor John Finlay said: "There has been a tragic farm accident and I would like to say that the family are in my thoughts. The whole of the community here has been calling me to voice their concern for the family."
First Minister Peter Robinson said in a tweet: "Tragic news coming from N Antrim tonight. My thoughts & prayers are with the family at the centre of this awful situation."
A spokesman for the Police Service of Northern Ireland (PSNI) said: "Police can confirm that the Health and Safety Executive are currently conducting an investigation into the circumstances surrounding a farming accident in Dunloy on Saturday, June 7.
"At the request of family members police will not be releasing any further details at this time."
In September 2012, Ulster rugby star Nevin Spence, his father Noel and brother Graham died after entering a slurry tank to rescue a dog at the family's farm outside Hillsborough, Co Down.