The force said re-opening crime scenes “is often standard procedure”.
The remains were discovered after a report to police two days earlier.
Det Ch Insp John Davies, who is leading the investigation, said it was “unlike anything I have come across during my policing career so far”.
He said: “I want to be clear, as to dispel any speculation, we do not believe there are remains belonging to any other parties at this property.
“It is being treated as an isolated incident.”
DCI Davies added the force was “keeping an open mind” as to how the remains came to be at the house and urged anyone with information to come forward.
