There have been no confirmed sightings of Daniel Khalife in the 36 hours since he escaped from prison, police say.
The Met Police commander leading the search said the former soldier and terror suspect was “very resourceful”.
The 21-year-old is accused of trying to spy for an enemy state, understood to be Iran, and plotting a fake bomb hoax.
Police have detailed the route of the delivery lorry Mr Khalife clung to the underside of to make his escape from HMP Wandsworth.
Cdr Dominic Murphy, head of the Met’s Counter Terrorism Command, confirmed that the vehicle Mr Khalife used to escape was stopped in nearby North Sheen in south-west London less than an hour after he was declared missing, and strapping was found underneath.
Detectives believe he was still wearing his prison-issue cook’s uniform when he slipped out of the category B prison.
Catering firm Bidfood confirmed one of their vehicles was involved and said their driver had “fully co-operated with the police”.
Cdr Murphy said it was a “little unusual and perhaps a testament to [Mr Khalife’s] ingenuity” that he has not been spotted, despite 50 calls from the public offering “valuable lines of inquiry”.
As a trained soldier “he has skills that perhaps some sections of the public don’t have”, he added.
Cdr Murphy said it could not be ruled out that Mr Khalife had help escaping and had access to money.
Some 150 Met Counter Terrorism Command officers have been deployed to the search since he was declared missing at 08:15 BST on Wednesday.
Mr Khalife is thought to have links with Kingston and the north-west of England, and the search is focused on London.
But Cdr Murphy said it was “absolutely possible” he may have already left the country, and security at ports and airports has been tightened.
Disruption continued at the Port of Dover on Thursday. Junctions eight and nine of the M20 were temporarily shut due to the enhanced checks.
Within hours of the escape, questions were being asked about why Mr Khalife was not being held in a high security prison and how he was able to slip through the net.
Justice secretary Alex Chalk has ordered two urgent reviews into the categorisation and placement of all prisoners at Wandsworth, and all those in custody charged with terrorism offences.
He told the House of Commons that Mr Khalife “will be found and he will be made to face justice”.
Shadow home secretary Yvette Cooper told the BBC that Wandsworth prison – which for the last few years has held 60-80% more prisoners than it was designed for – has long been known for its overcrowding and staffing issues.
She said the escape shows “there has been a failure”, adding: “Any government has to make sure national security is taken immensely seriously and ministers need to respond to warnings that are given to them.”
Mark Fairhurst, chairman of the Prison Officers’ Association (POA), said the union had been saying since 2010 that “cuts have consequences”.
John Podmore, who ran Belmarsh and Brixton prisons, told the BBC’s World at One programme that there was a possibility the escape was an inside job.
He said Mr Khalife “should have been in Belmarsh” – a high security prison in south-east London.
Sue Sim, former chief constable of Northumbria Police who led the manhunt for Raoul Moat, told BBC Radio 4’s PM programme the escape appeared to have “an element of organisation”.
“Particularly so now the commander has said they have had very few sightings,” Ms Sim said. “That means somebody was waiting for him probably, and they’ve been able to move him on to somewhere which is a safe place.”
Mr Khalife joined the Army in 2019 and was based at MoD Stafford – also known as Beacon Barracks – when he disappeared on 2 January after an alleged bomb hoax.
A later court hearing at Westminster Magistrates’ Court heard he allegedly planted fake devices “with the intention of inducing in another the belief the item was likely to explode or ignite”.
He was arrested “in or near his car” on 26 January after “active efforts to look for him”, a court heard. He was placed in Wandsworth two days later.
Mr Khalife was due to appear in court on 13 November to face charges including preparing an act of terrorism and collecting information useful to an enemy.
He denied the charges against him at the Old Bailey in July.