A second man has been arrested following four potentially linked stabbings in the Edmonton area, Scotland Yard have said.
A man in his 40s was arrested at a residential address in Edmonton on suspicion of GBH and taken into custody at a north London police station.
Police said another man, who was arrested on suspicion of GBH on Sunday at 10.53am in Fore Street, remains in custody.
Two of the victims - a woman and a young man - are still fighting for their lives in hospital as police try to urgently ascertain who the attacker was.
Police believe a single male suspect was acting alone and that "mental health issues may be a factor".
The Met said it remains a live investigation and said they are pursuing all lines of inquiry, as they advised members of the public to remain vigilant.
Police had been hunting a single male suspect, described as a black man, approximately 6ft 3ins, of skinny build and wearing dark clothing, possibly a hooded top.
Enquiries continue to establish if either is the individual behind these incidents.
- What is the timeline of the attacks?
The first stabbing took place at 7.02pm on Saturday at Aberdeen Road following reports of an assault.
The 45-year-old victim sustained a stab wound to her back after being attacked by the man.
She was taken to an east London hospital where she remains in a critical condition.
The second incident took place four hours later at around 12.15am on Sunday morning with reports of a male suffering stab injuries in Park Avenue.
Officers and London Ambulance Service attended and the 52-year-old man was taken to an east London hospital for treatment.
His condition is not life threatening.
The third incident on Sunday was at 3.55am with reports of a man stabbed at Seven Sisters Tube station.
A 23-year-old man suffered stab injuries and remains in hospital in a critical condition.
Initial enquiries established that the man may have sustained his injuries in Silver Street, Edmonton.
The last incident took place at 9.43am in Brettenham Road.
Officers attended and found a man with a stab injury to the back.
He has been taken to hospital for an assessment of his injury, and while his injuries are not life-threatening they are potentially life-changing.
- How residents have reacted
Dervish Husseyin, 60, was at his friend's house on Aberdeen Road when the stabbing took place.
"I seen the woman lying down, face down," he said.
Mr Husseyin said the woman had "blood on her back" but did not seem to realise she had been stabbed.
"She said she only went out for a walk on her own," he said.
Natasha Cameron, 45, lives on Aberdeen Road and was walking home from work at a nearby casino after 10pm.
She said she saw officers on her road who told her there had been a stabbing but she was unaware of the later attacks.
"I was 'oh my God this is the road I live on'," she said.
Ms Cameron added: "I'm scared now because I always walk here from work home.
"Now I'm definitely taking the bus."
- What have police said about the stabbings?
Detective Chief Inspector Stuart Smillie from North Area Command said: "We are doing everything we can to apprehend the suspect behind these cowardly and senseless attacks.
"We are treating the four stabbing related incidents as potentially linked.
"The four victims are from different backgrounds and appear to have been selected at random due to them being alone and vulnerable.
"There is nothing to suggest this incident is terror related.
"We are working on the hypothesis that the single male suspect is acting alone and mental health issues may be a factor.
"All of the people he has targeted have been walking alone and he has approached from behind without warning.
"The motive from the stabbing appears to be solely to inflict harm.
"Early accounts suggest none of the victims were robbed or engaged in conversation before they were attacked."
Police said inquiries continue to establish the attacker behind the incidents, and until that is determined, enhanced police activity will continue in and around the area.
Police tape was up and officers were calling at houses along Aberdeen Road on Sunday afternoon accompanied by a police dog.
Officers in forensic suits could be seen along the stretch of road within the police cordon.
“Extra resources have been called upon and are on the streets now working to keep the public safe and catch the individual responsible,” Scotland Yard said.
- More powers for stop and search
In a bid to tackle the country's knife crime crisis Home Secretary Sajid Javid has granted police more powers to stop and search.
Currently, officers can only use stop and search powers when they believe serious violence "will" take place.
Under the new changes, brought in by Mr Javid, an officer only has to believe serious violence "may" occur.
Mr Javid described the changes as a "vital tool" to tackle serious violence.