The incident occurred when a basin at the slaughterhouse overflowed, causing waste to seep out into a nearby stream in Skövde, reported the Skaraborgs Allehanda newspaper.
Subsequent tests showed that the stream's levels of ammonia nitrogen, which can be poisonous to humans, were ten times higher than the legal limit. But it was the abattoir's tardiness in reporting the spill that really upset the local environmental authorities, who said that the three days it took to alert them was far too long.
The head of the slaughterhouse, Ove Konradsson, said he couldn't be blamed for raising the red flag three days later. He said his team had discovered the leak within 15 minutes and put a stop to it straight away.
"But it was Walpurgis weekend, the authorities were closed for three days and we couldn't even call them," he told The Local about the incident which took place in late April.
"What were we supposed to do? Go over to their house and knock on the door?"
He thought about 15 litres of blood had leaked into the nearby brook, a volume he described as "about as much blood as in a calf".
"That's enough to colour 1,000 litres of water," he said.
The case has now been handed over to the prosecutor's office.