Police have reiterated that there is "no wider threat" and continue to treat yesterday's stabbing as an "isolated incident".
A 16-year-old boy remains in a London hospital after he sustained stab wounds in Leeming Road, Borehamwood, yesterday afternoon.
Police cordoned off the Co-op store following the incident which happened shortly before 1.45pm.
The victim was taken to hospital where his condition is currently described as serious but stable.
A forensic officer was seen working at the front of the Co-op store, but police had left the scene by 6pm.
No arrests have been made in connection with the stabbing but police believe the victim and attacker are known to each other.
Detective Sergeant Gemma Badat, who is investigating, said: "We are aware that incidents of this nature are always going to cause concern in the local community, but I would like to take this opportunity to reassure the public that we do not believe there to be any wider threat, and we are treating this as an isolated incident.
"The victim and the suspect(s) are believed to be known to each other.
"Enquiries are ongoing, and I’d like to ask anyone who witnessed the incident, or anyone who believes they have any information they think could assist with the investigation, to get in contact as a matter of urgency."
Anyone with information is asked to contact 101 quoting reference Op Catalyse or call Crimestoppers anonymously on 0800555111.
Shortly after the stabbing, Cowley Hill ward councillor Michelle Vince says she had been 'fearing' an incident like this for a while.
Cllr Vince and her colleagues have previously raised concerns about antisocial behaviour and the threat of knife crime in the Leeming Road area.
In September, Hertfordshire Constabulary were granted special powers to stop and search individuals without any reason to do so in the Cowley Hill ward - at the time Inspector Mark Bilsdon said this was on the back of intelligence which suggested there may be disorder in the town involving weapons.
On August 10 last year, multiple armed police units were called to the Leeming Road area and surrounding streets after cameras captured a group of males walking around with knives.
Police in Morpeth Avenue back in August responding to an emergency call
Cllr Vince said yesterday: "Last summer, I said I was terrified that there was going to be a stabbing in Leeming Road. I’ve been fearing this. It’s a very sad day for Borehamwood.
"Myself, Cllr Jeremy Newmark, and Cllr Richard Butler are going to ask to meet the inspector as councillors this week.
"There were measures put in place previously to make Leeming Road safer and we will ask for these again. We need a stronger police presence here."
Police have added that an incident in Northgate Path at lunchtime today is not being linked to the stabbing.
A man in his 20s sustained cuts to his hand after burglars wearing balaclavas forced their way into a home. One was reportedly armed with a knife.
Sergeant Chris Payne, who is investigating, said: "Firstly, I’d like to stress that this is not being linked to the incident that happened in Leeming Road yesterday. We understand that incidents of this nature are alarming, and will undoubtedly cause concern amongst the local community.
"Please be assured that we are carrying out extensive enquiries to identify the offenders. If you were in the area around the time and believed you may have witnessed the incident, or believe you may have seen anyone in the area behaving suspiciously, please get in contact.
"Any information, no matter how minor or insignificant it may seem, could be vital to us solving the case."
Anyone with information is asked to contact Sergeant Payne directly via email at Chris.Payne@herts.pnn.police.uk
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