Water Damage From Neighbours Property

We recently bought a property in Camposol and, have realized that there is a big hole in the ground on my neighbours property allowing torrential rainfall to enter our under build and damage the piles and ground. Our house is sinking due to the undermining of the foundations and ground. We have been told a denuncia on the property owner is the best way forward however, no one knows who the house owner is? Has any one got any advice?