Police searching for Latvian builder Arnis Zalkalns – the prime suspect in the murder of London schoolgirl Alice Gross – have found a body, sources said.

Alice, 14, of west London, was last seen walking home on August 28. She was seen by CCTV cameras walking beside a canal.

Zalkalns, who had been convicted or murdering his wife in Latvia before he moved to England, was filmed passing by a few minutes later – but had not been seen since September 3.

Alice was last seen on CCTV walking along the towpath beside the Grand Union Canal near her home on the afternoon of August 28.

Nearly three weeks later investigators realised that Zalkalns, who was reported missing by his family on September 5, had been cycling behind her.

He served seven years in prison in his native country for bludgeoning and stabbing his wife Rudite to death.

The general labourer, who worked at a building site in Isleworth, west London, is believed to have come to the UK in 2007, but authorities here are thought to have had no record of his murder conviction.

Alice’s disappearance prompted an outpouring of support in her local community, where yellow ribbons and bows still adorn the streets.

David Cameron has said he will examine “all the circumstances of the case” surrounding the murder of Alice, whose body was recovered on Tuesday.

The Prime Minister has described it as a “horrific case”, and said: “Anyone with a daughter will have just felt sickened by what has happened and what that poor family has had to go through.”

He continued: “I will look at all the circumstances of the case: what lessons there are to learn, whether that is about exchanging information or whether that’s about the importance of keeping our country safe. I am going to look at that and I will come back to you.”

Mr Cameron’s words came after it was revealed that further tests will be carried out on Alice’s body after a post mortem examination proved inconclusive.

The post-mortem at Uxbridge mortuary took two days due to the “complex nature” of the investigation, Scotland Yard said.

In a statement, police said: “No cause of death has been given at this time and further tests are required.”

Julian Bell, leader of Ealing Council, said talks would be held with the family at a later stage over the prospect of a permanent memorial.

Hundreds of messages were added to a book of condolence set up in Ealing town hall. He said people “queued out the door” at one stage as they waited patiently in line to pay their respects.

The book will eventually be passed on to Alice’s family, while flags in the area were also flown at half-mast as a mark of respect.

Alice’s parents, Rosalind Hodgkiss and Jose Gross, said in a statement: “We have been left completely devastated by the recent developments and it is difficult to comprehend that our sweet and beautiful daughter was the victim of a terrible crime.

“Why anyone would want to hurt her is something that we are struggling to come to terms with.”

The Metropolitan Police have come under fire for delays in identifying Zalkalns as a suspect, and were not able to apply for a European Arrest Warrant due to lack of evidence.