Police searching for missing schoolgirl Alice Gross have found a body hidden in a river near her West London home.
Scotland Yard said the case is now being treated as a murder inquiry.
Officers said 'significant efforts' had been made to hide the body found in the River Brent in West London on Tuesday (30 September).
The 14-year-old's family have been informed of the development.
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Alice was last seen on August 28 walking along the Grand Union Canal towpath towards her home in Hanwell.
CCTV showed a Latvian convicted killer, Arnis Zalkalns, cycling past the same spot 15 minutes later and he has become the prime suspect in her disappearance after he went missing on September 3, but police have been unable to trace him.
Officers said 'significant efforts' had been made to hide the body found in the River Brent in west London on Tuesday evening.
In a statement, Commander Graham McNulty, who has been leading the investigation, said: "Last night, 30 September, a search was carried out in the River Brent, as part of our ongoing investigation into the disappearance of Alice Gross.
"Following this search we have sadly recovered a body from the water.
"This is obviously a significant development and Alice's family has been informed.
"We are unable to make a formal identification at this stage, but clearly this news is devastating for everyone involved in the search for Alice.
"At this time my thoughts are with Alice's family and friends. I would ask you to respect their privacy and allow them space.
"This is now a murder investigation and I need the public's help to find whoever is responsible.
"I would urge anyone who may know something to come forward. Even if you have not yet spoken out it is not too late to tell us what you know.
"I would like to thank the local community of Ealing who have shown huge support and patience during the course of our investigation. This discovery will have a significant impact throughout the borough.
"You only need to walk around the surrounding streets to see the effect that Alice's disappearance has had on the whole community.
"Our work at this scene is crucial to ensure we capture all the available evidence allowing us to identify who is responsible for this dreadful crime.
"This may take some time, and I ask people to remain patient with us.
"I can confirm that significant efforts were made to conceal the body.
"At this point I do not wish to speculate any further on what has happened.
"Finally, I would like to reiterate my request that Alice's family and friends are given the time to come to terms with this news. My thoughts, and those of all of us in the Metropolitan Police, are with them at this difficult time."
Scotland Yard are working with officials in Latvia to try and trace Zalkalns, who served seven years in prison for stabbing his wife Rudite to death.
However, they have admitted that they would have no power to arrest him if he is found because they currently do not have enough evidence to issue a European Arrest Warrant.
Zalkalns, 41, who worked at a building site in Isleworth, west London, is thought to have come to the UK in 2007, but authorities here apparently had no record of his murder conviction.