Thames Valley Police have issued the following statement.
UPDATE - Human remains found at location of Leah Croucher investigation
"Following information received from a member of the public on Monday relating to a property in Loxbeare Drive, Furzton, Milton Keynes, specialist officers and forensic teams from Thames Valley Police attended the location.
"As a result of an ongoing detailed forensic search of the property, a number of items have been located.
"During the search we have found items, including a rucksack and personal possessions belonging to Leah Croucher, who was reported missing on 15 February 2019.
"As a result of our findings, we have now launched a murder investigation.
"This is a complex and challenging scene, which we have been at since just after 6.30pm on Monday.
"We will continue to be at the scene for a significant period of time.
"A large-scale missing person investigation has been ongoing for the last three and a half years, with extensive searches and house-to-house enquiries."
Thames Valley Police Head of Crime, Detective Chief Superintendent Ian Hunter said: “Following a call to us on Monday, we attended an address and located items of concern within the property.
“We are dealing with a very difficult scene but we can now confirm that we have discovered a number of items that are linked to Leah, and as such, we have now launched a murder investigation, led by our Major Crime Unit.
“Leah’s family have been kept updated and continue to be supported by officers, and we are urging the public and media to think of her family and not to speculate further while this investigation is in the early stages.
“We will provide further updates when we are able to do so.
“There remains a scene-watch in place at the address while this investigation continues, and we are committed to ensuring that our enquiries at the scene are thorough.
“During our search for Leah, we have committed hundreds of officers and staff to the search for Leah over the last three and a half years, reviewing 1,200 hours of CCTV and conducted more than 4,000 house-to-house inquiries and offered several rewards for information to lead us to Leah.
“The call from the member of the public that we received on Monday was the first occasion that we were alerted to this address, and we thank them for contacting us immediately to report their concerns.
“Our thoughts remain with Leah’s family and friends, and we will continue to offer them all the support that they need.”