Investigators have begun to examine a slurry container which burst on a Co Down farm, drowning two men in up to 500,000 litres of chicken slurry.
The bodies of James Wilson (21), an agriculture student from Cloughmills, and James Blair (33), a farm worker from Rasharkin, both in Co Antrim, were retrieved from the site at Katesbridge by specialist rescue workers after the accident on Tuesday.
The Dutch-made slurry container, about 22 metres long and 1.5 metres high, burst as it was being filled with waste being delivered by a container lorry.
The driver tried to call one of the victims by mobile phone once he realised the tank had burst.
Police and the Health and Safety Executive have launched separate investigations to establish the cause of the accident.
Mr Wilson was to have graduated in agriculture from Queen's University, Belfast, early next month.
Yesterday, his father Robin said: "It's hard to believe he has been taken away from us. We just found a note in an envelope which James had been due to post back to Queen's for the graduation."
Both victims were understood to have been hired to help a Co Antrim-based contractor. They were working on farm land leased out by Jackie Porter, a retired dairy farmer.
Mr Porter was not present at the time.
He said: "They were filling it and emptying other stuff at the same time. I was told the boys were standing right beside the container when it happened. A lorry driver was there and he's just in a daze now."
Banbridge SDLP councillor and farmer Séamus Doyle said: "They were out doing their day's work and this was just a tragic accident. It was a lovely day yesterday - it was a great pity that two young men lost their lives."