Police investigating the murder of Rory Blackhall have reconstructed the moment he was dropped off by his mother to go to school in Livingston.
A black car similar to that of Rory's mother was placed at the bus stop
A black Vauxhall Meriva car was parked exactly a week ago at the bus stop where Rory, 11, was left by his mother to walk to Meldrum Primary.
Police have revealed that a blonde woman who was in the area at the time has now come forward.
Two assemblies have been held at the school to remember Rory.
His body was found in woods near the school on Sunday, three days after he went missing on his way to school. He had been asphyxiated.
During the reconstruction an identical black Vauxhall Meriva car was driven along Deans East Road in Livingston at 0830 on the route Rory's mother would have taken when she dropped him off.
It stopped in the lay-by for 20 seconds and then continued to the mini -roundabout near the school when it then came back along Deans East Road.
A team of 24 officers was situated at various locations near the underpass which Rory walked through to get to school and footpaths.
Some 160 questionnaires were filled in by members of the public, including school pupils. These are now being studied by police.
Letters from the police are being handed out to 10,000 pupils in Livingston, acknowledging people's fears but reassuring them that high-visibility patrols are in place and that crimes of this nature are rare.
A new poster appealing for information is being circulated, displaying a picture of Rory taken in school uniform in April.
Chief Inspector Jim Thompson of Lothian and Borders Police told BBC Radio Scotland they had not considered it appropriate to use a child like Rory in the mini-reconstruction.
He said: "We've used the same type of car as used by Rory's mum and we are hoping that it will jog someone's memory of having seen a similar car stopping at the bus stop.
"There's a 76-hour gap from the time he was dropped off to the time his body was found."
He added: "A male cyclist, who was in the area and saw a boy matching Rory's description walking in a direction opposite from Meldrum Primary School, also saw a blonde woman standing at a nearby bus stop and we are pleased to say that she has come forward.
The picture of Rory, taken in April, which is on the new posters
"We will be interviewing her today."
He also appealed for members of the public with any information, no matter how insignificant, to get in touch.
"We still need that vital clue," he said.
Police have now received 650 calls to their incident helpline.
More than 300 children and staff attended two half-hour special assemblies at Meldrum Primary, which were led by acting head teacher Barbara Gregor and the school chaplain, the Rev. Graham Smith.
Ms Gregor said: "Some of the older children were naturally a bit upset but we all took comfort from the minister's words.
"We have received various floral tributes, including a lovely display from the local old folks home, which was a really nice gesture. We have received cards and messages from all over the country and overseas and they have been a great comfort.
Floral tributes have been sent to the school
"We are trying to maintain our school routine under difficult circumstances. We very much appreciate all the support we are receiving from the wider community.
"It gives a clear message to the children that it is all right to feel sad at this time. We are all here for each other as a school family."
Pupils and teachers have been among the hundreds of mourners who have placed flowers, cards and soft toys at the end of the path through woods where the youngster's body was found. He had been covered with an old tent.
The school has faced criticism for not alerting Rory's parents when he failed to turn up for class.
The local authority said it intended to look at reviewing the policies it had in place.
A spokesman said: "When all the facts are known, we will examine our existing policies and procedures to see if any lessons can be learned.
"We will do this in consultation with parents and the police and we will take full account of any national guidance that might be forthcoming."
He added: "The council's main focus is on dealing with the immediate repercussions of Rory's tragic death by providing support and reassurance to pupils in our schools and the wider community."
A dedicated email address has been set up by police appealing for information. It is firstname.lastname@example.org.