Police have arrested a second man over the fatal stabbing of teenager Jodie Chesney in an east London park.
The suspect was arrested in London on Friday morning on suspicion of murder.
Police have given no other details about the man.
A 20-year-old man arrested in Leicester on Tuesday remains in custody.
Ms Chesney was approached by two males and knifed in the back while she listened to music with friends near a children's playground in Harold Hill.
Detectives had said investigators were "focusing totally" on a witness appeal to try and track down the suspects.
Detective Chief Inspector Dave Whellams, who is leading the investigation, said: "This was a savage, evil attack. We're progressing well with the investigation and continue to ask the public to assist us.
"At this time, there being no clear motive is very unusual. We retain an open mind and can't rule anything out.”
Ms Chesney is one of 17 people to be fatally stabbed in London this year.
On Thursday evening, thousands of people marched through Romford town centre to remember the 17-year-old and protest against the spate of knife killings.
Demonstrators wore purple - Ms Chesney's favourite colour - and chanted "no more knives" during the march on Thursday evening.
Speaking at the march, a friend of Ms Chesney's family said “This march shows the ripple effect that knife crime has. It touches all of our lives."
Ms Chesney's father, Peter, has called for mandatory sentences for those carrying knives as he paid tribute to his "kind, good and thoughtful" daughter.
