The skeletal remains, which are those of a man and are thought to date back two years, were uncovered by workmen in Warfield, at about 4pm on Friday.
A post mortem took place yesterday but was inconclusive.
Detective Superintendent Nora Holford, of Thames Valley Police, said: “Due to the fact that these skeletal remains are thought to be at least two years old, this is set to be a long and complex investigation.
“At this stage we believe the remains were placed in Hawthorn Hill a number of years ago.
“Our enquiries are ongoing to establish the circumstances surrounding the death and how the remains came to be left in Warfield.
“We are also working to identify the deceased but due to the length of time we believe the remains have been here, identification may take longer than usual.
“A scene watch and a forensic tent remain in place while officers continue enquiries today.”