Two more people have been arrested in connection with the murders of two teenagers.
Max Dixon, 16, and Mason Rist, 15, were attacked in Knowle West, Bristol, at about 23:20 GMT on Saturday. They later died in hospital.
A 44 year-old-man and 15-year-old were arrested in connection with the stabbing at the weekend.
A third man, 20, was arrested on suspicion of murder and a 22-year-old man was arrested this afternoon.
Speaking at a news conference on Monday, Bristol Police Commander Supt Mark Runacres said: "I don't believe this is rooted in gang warfare.
"I understand the impact this incident has had, I'm a dad myself - but we've seen the strength of the community."
The boys were attacked by a number of people, sustained stab wounds and were taken to two hospitals - Southmead Hospital and Bristol Royal Hospital for Children - by ambulance, where they died in the early hours of Sunday morning.
About 200 people attended a vigil on Sunday evening where the teenagers were attacked in Illminster Avenue.
Members of the community came to light candles and lay flowers.
GoFundMe pages have been set up to help with the funeral costs for the two teenagers, which have raised more than £2,000.
"Any death is awful, but the loss of Mason and Max, who had their whole lives in front of them, is particularly tragic and my heart breaks for the families who have to endure such unimaginable pain and suffering," Supt Runacres said.
Supt Runacres added he could not confirm whether the suspects and victims were known to each other or whether the killings were a case of mistaken identity.
He said: "That is something we are continuing to investigate to understand any links that do exist."
Detectives have not recovered any weapons.
High-visibility patrols are now being carried out to provide reassurance to the community while enquiries are conducted, police said.
More than a hundred officers are involved in the investigation, including officers which have been drafted in from other forces, Supt Runacres added.
"Our investigation is progressing well, with four people arrested so far and more arrests are to come.
"We are committed to doing everything we can to hold to account those responsible for this horrendous crime and to provide answers to Max's and Mason's families," he said.
Supt Runacres told the press conference he was keen for families to carry on as normal.
"I would ask parents to get their kids to school," he said.
"It's a safe place to be and it's important to attend, but we also understand their concerns.
"Officers are working with schools to keep them informed and to give reassurance."
Both teenagers were pupils at Oasis Academy and Principal Victoria Boomer-Clark described their deaths as a "tragic loss of life in a really senseless event".
She added: "We have two wonderful young men, Max and Mason who were only 15 and 16 years old.
"They have family, they have friends, they have loved ones. They had bright futures ahead of them and now they're gone.
"At this incredibly difficult time our heart pours out to the families."
Local resident Carol Casey said there was anger in the community over what had happened.
"We're very angry at what's going on. We've been trying to get the old youth club back in the area for years.
"It's a very sad thing for the parents. We need the youth club back for these kids."
Marvin Rees, the mayor of Bristol, said the incident was a "tragic loss of life".
"I'm thinking of the victims and their families, going through a pain that no parent should have to experience," he said.