Three men died and a woman was injured after they fell into a slurry tank at a farm at Hillsborough in Northern Ireland.
Emergency crews raced to the scene on Drumlough Road outside the Co Down village after the alert was raised at 6pm.
But following a lengthy rescue operation police confirmed three men had died and a woman was taken to hospital for treatment.
An officer said: "The health and safety executive have been notified and will carry out an investigation in due course."
The men killed in the tragedy are believed to be two brothers and their father.
The Northern Ireland Ambulance Service (NIAS) said it responded to a 999 call at approximately 6.15pm following reports that at least three people had fallen into a slurry tank. It said it immediately despatched three Rapid Response Paramedics, four Accident and Emergency vehicles and an ambulance service doctor to the scene.
The Northern Ireland Fire and Rescue Service was also in attendance and rescued four people from the slurry pit.
A spokesman said: "Three were unconscious and NIAS paramedics commenced resuscitation efforts immediately assisted by other ambulance personnel. One of the four showed initial signs of responding to the efforts of the crews and was transported immediately to the nearby Lagan Valley Hospital, where unfortunately he died a short time later.
"Despite the best efforts of all involved the other two men died at the scene. A female was treated at the scene and taken to the Royal Victoria Hospital where she is recovering from the effects of fume inhalation."
The ambulance service said it extended its sympathies to those involved.