Thehas been called "pre-planned" by London's police chief as a wide-scale manhunt to find the terror suspect enters its third day.
Mark Rowley, the commissioner for London's Metropolitan police, told U.K. radio station LBC on Friday that police authorities were not ruling out the possibility that Khalife had assistance from others, including those working in the prison.
"To work out a prison escape, and how you are going to do the logistics of it, get the right equipment and how you are going to do it, it's unlikely that you would do that in the spur of the moment," Rowley said.
The 21-year-old former British soldier, who had been awaiting trial at a south London prison on terrorism related charges accusing him of planting fake bombs at an army base, escaped a London prison Wednesday by clinging to the underside of a delivery truck.
Khalife also faced charges of allegedly working for Iran and eliciting personal information from a U.K. Ministry of Defence database, according to CBS News partners at the BBC.
The search for Khalife narrowed on Friday as authorities honed their search in on Richmond park in southwest London — the largest urban park in Europe, spanning an area of 2,500 acres.
About 150 counter-terrorism officers are involved in the search effort, the Metropolitan police have said.
Police helicopters were seen circling the park overnight and vans were seen driving through the park on Friday morning.
There have been no publicly confirmed sightings of Khalife, and police have warned that the terror suspect may be more skilled at avoiding being caught due to his military background.
Investigators say that Khalife was last seen wearing a white T-shirt, red and white checkered trousers and brown steel- toe cap boots, and they believe he is still wearing a prison chef's uniform as he had worked in the prison kitchen while incarcerated.
Questions have been raised over whether Khalife should have been held in a more secure facility, considering the nature of the charges against him. London's Wandsworth prison where Khalife was held is a "Category B" prison, which holds high security prisoners but is not considered as secure as a "Category A" prison, the highest security ranking for prisons in the U.K.
Dominic Murphy, counter-terrorism commander for London's Met police, had confirmed that the vehicle Khalife used to escape had been stopped in southwest London less than an hour after he was declared missing, but Khalife had not been found at that time.
Murphy said on Thursday that despite over 50 calls from the public offering "valuable lines of inquiry," it was "a little unusual and perhaps a testament to [Mr Khalife's] ingenuity" that he has yet to be found.
for more features.