Police still have "no idea" why a 17-year-old girl stabbed to death in an east London park was targeted.
Jodie Chesney was with friends near a children's playground on Harold Hill when she was approached by two males and knifed in the back in a seemingly motiveless attack.
Jodie was pronounced dead just over an hour after police were called to the park at 9.25pm on Friday evening.
The suspect who attacked Jodie is described as a black male aged in his late teens, the Metropolitan Police said on Sunday.
There was no description given of the other male who approached Jodie and her five teenage friends while they were playing music.
The group were aware of the two males being in the park and saw them leave at around 9pm, police said.
The males returned around 30 minutes later and walked towards the group where one stabbed Jodie in the back.
The pair then ran off in the direction of Romford Road.
Detective Chief Superintendent Shabnam Chaudhri, who is leading the police response to the murder in the local community, said on Monday afternoon: "We still don't have any idea (why Jodie was attacked)."
She said investigators were "focusing totally" on a witness appeal to try and track down the suspects.
The Met has asked anyone who may have CCTV or dash cam footage between 7pm and 11pm on March 1.
Ms Chaudhri refused to speculate on whether the attack could have been some form of gang initiation.
She said the Met's Violent Crime Taskforce had been deployed in the Havering area as well as additional patrols in the boroughs of Redbridge, Barking and Dagenham and Havering.
"We are working robustly - not just here but across the whole of London," she said.
"We've increased overtime, we've extended the number of officers on shift we've seen an increase in stop-and-search.
"We've carried out over 2,500 stop-and-search in the last few days, so we are working very robustly."
When asked if the Met needed more officers, she replied: "I'd love to have more officers but I have to work with the numbers that I've got."
A post-mortem carried out on Sunday established that the cause of Jodie's death was trauma and haemorrhage, and police released a photograph of the teenager on the same day.
Jodie was a Girl Scout and school friends said students at Havering College would be wearing purple next Friday in honour of Jodie and her Barking & Dagenham scout troop colours.
She posted a photograph on Instagram with fellow scouts at 10 Downing Street on Remembrance Day last year, with the caption: "I'm basically famous now ... this was such a good opportunity and so much fun."
Reverend Alan Moss, 37, who had come to lay flowers for Jodie said a lot of young people had been relocated to the borough out of inner city areas to try and break the cycle of gang violence.
Rev Moss, of nearby St Johns and St James' Church, said: "It's not really solving the problem, it's just moving it.
"There were a lot of people who weren't gang affiliated who now are."
He continued: "Of course this may not have been gang related, it could have just been a random attack."
Rev Moss did not know Jodie personally but works with young people in the community.
A charity set up a fundraising page for Jodie's family which raised more than £4,000 of the £5,000 goal in a day.
It said: "The whole community are still trying to come to terms with this shocking event.
"As a local charity we want to support the family as much as we can to alleviate the financial stress on this young lady's funeral."
Two school friends told the Press Association they were "disgusted" by the killing. One said: "Jodie had no enemies, she was the nicest person."
Jodie's uncle Dave Chesney told ITV News on Sunday that the family had lost a "beautiful, lovely and quirky" girl.
Posting on Facebook on Saturday, Jodie's grandmother Debbie Chesney said too many young people were having their lives "cut short by needless violence".
She echoed calls for people to come forward with information.