NI Water has moved to reassure customers that there is no risk to water supply following the discovery of nine dead horses.
The animals were found in a field owned by the utility company near Banagher Forest in Co Londonderry.
However, the firm said the remains have not contaminated rivers feeding Caugh Hill Water Treatment works, which supplies drinking water to the surrounding area.
Animal welfare officers last week launched an investigation after the bodies of three horses were discovered in a field in the Feeny area. Six other horses, believed to have been abandoned in the field by their owner, were seized by welfare officers and were in a "horrifying state".
In subsequent searches by locals of the 150 acre field on the Glenedra Road near Feeny, one horse was found dead with a gunshot wound to his head and five other horse corpses were uncovered, as well as a mound of horse limbs and body parts.
NI Water confirmed that the land the horses were abandoned and died on belonged to them. They said there is no risk to water supplies.
"NI Water can confirm that there is no risk to the public water supply following the discovery of animal carcasses on NI Water owned land," a spokesman said.
"The location of the animal remains is well away from the Glenedra River, and recent samples do not show any abnormal trends for the raw water source.
"Arrangements are being made to remove the animal remains. The treatment processes at our nearby Caugh Hill Water Treatment works are designed to be able to deal with such pollution or contamination had it occurred, without there being any risk to the public water supply served by Caugh Hill Works."
Local horse owner Teresa McKenna, who has been searching the land for remaining abandoned animals, says some of the corpses may have been tampered with in a bid to hide ownership.
"One of the horses we had discovered last week had since been burned. Someone took petrol to it and attempted to burn it in a bid to destroy its microchip, which would identify its owner."
Causeway and Glens Council said: "We can confirm a total of eight horses are in the care of council, each of these horses have received veterinary attention and are being well cared for."