People living near to where a boy was stabbed to death have been asked to search their gardens for the weapon.
Paul Erhahon, 14, died outside his home after he and a 15-year-old friend were attacked by a gang in Leytonstone, north-east London, on Friday.
Police said a bladed instrument or a knife was used to kill Paul and injure his friend, who remains critically ill.
Local churches are to pause during Easter services to remember Paul. Two youths are being held over the attack.
A 13-year-old boy and a 19-year-old man were arrested in the early hours of Saturday and remain in police custody.
A neighbour said Paul's mother found her son slumped in Crownfield Road, where he and his friend had staggered after being stabbed repeatedly at a block of flats nearby.
"He was barely moving, but he was going into unconsciousness and he could not speak. She was screaming blue murder," Elizabeth Chapkins said.
"I don't want to hear or see anything like that again. There was nothing we could do."
Graffiti reading "RIP Paul" has been sprayed near Paul's home.
Numerous messages have also been sent his MySpace website page, which he had created under the name Hellrazor.
His music and a link to a YouTube film of a group he was in called The Funeral Soldiers is also featured on the page. In the film his name appears as Hell Reiser.
LONDON'S TEENAGE VICTIMS
James Andre Smartt-Ford, 16, shot in Streatham, 3 February
Michael Dosunmu, 15, shot in Peckham, 6 February
Billy Cox, 15, shot in Clapham, 14 February
Kodjo Yenga, 16, stabbed in Hammersmith, 14 March
Adam Regis, 15, stabbed in Plaistow, 17 March
People living in the area have voiced fears about a rise in gang culture among young people and a residents group was set up last year to tackle the problem.
Police have said they are investigating whether Paul's death was gang-related but are keeping an open mind.
Det Ch Insp Matthew Horne said they understood that a large group of youths had been involved in an incident in the foyer of Gean Court, a block of flats in Langthorne Road, during which they thought the two boys had been stabbed.
"It is believed they then managed to stagger the short distance to nearby Crownfield Road," he said. "A number of youths were seen running from the scene."
Officers are reviewing CCTV footage.
The latest attack follows the killing of five other male teenagers in London in the past two months.