A second suspect is being questioned over what police have said was the racially-motivated murder of black A-Level student Anthony Walker.
The 18-year-old was attacked with an axe by a gang of up to four white men in Huyton, Merseyside, on Friday.
A 17-year-old was being held by police on Monday and a man, aged 18, arrested on Sunday has been released on bail.
Det Ch Supt Peter Currie, of Merseyside Police, said the attack was "despicable and abhorrent".
The force has had more than 50 calls about the murder, but said it needed more information.
Mr Currie added: "I would urge anyone else who has information but hasn't yet made that call, please pick up the phone and tell us what you know.
"I would like to reassure the community that we will not rest until those responsible for taking Anthony Walker's life are brought before the courts."
Mr Walker was beaten up weeks earlier, but his family did not report it as he was with a white friend at the time and they did not consider it racially motivated, Merseyside Police said.
Local MP Edward O'Hara has dismissed comparisons between the attack and the murder of Stephen Lawrence.
The Labour MP for Knowsley South said there were important differences between Mr Walker's killing and the murder of Mr Lawrence in Eltham, south-east London in 1993.
He told the BBC Radio 4 Today programme: "There is a certain surface comparison but this act was random, exceptional and representative of absolutely nothing."
'Talk to police'
Mr O'Hara said it was a racist attack but "entirely untypical of the community in which it happened".
Mr Walker's mother Gee has said her son was killed "purely because of the colour of his skin".
And Mr Walker's sister Dominique, 20, has appealed for people to help catch the gang who attacked her brother in McGoldrick Park on Friday night.
"If anybody knows anything, they have got to talk to the police," she said.
"Talk to them because we need the information. I need to find out who did this to my brother."
Dozens of floral tributes have been left at the scene of the attack
Miss Walker said her brother loved playing football and was an Arsenal fan, but his main sport was basketball and he had trials for the Liverpool and England basketball teams.
"He was a very kind, loving, caring, young man. He gave so much of his life to help other people," she said.
Stephen Lawrence's mother Doreen Lawrence OBE said Mr Walker's murder was "senseless" and a "loss to society".
"All the staff and trustees of the Stephen Lawrence Charitable Trust offer their deepest sympathies and condolences to Anthony Walker's family during this time of great anguish and loss," she added.
Mr Walker had spent the evening with his white girlfriend before the attack.
Axe in skull
Merseyside Police said that as the couple waited for a bus outside the Huyton Park pub with Mr Walker's 17-year-old cousin they were subjected to a "torrent of racial abuse" by a man in his 20s wearing a hooded top.
They did not retaliate to the abuse and left to find another bus stop. But they were followed and, as they walked through a park, they were attacked by a gang of up to four men.
Mr Walker's girlfriend and cousin ran to get help. When they returned Anthony was slumped on the ground with massive head injuries.
An axe was found embedded in his skull.
A book of condolence was due to be opened at Mr Walker's local church, the Grace Family Church, in Aigburth, on Tuesday.
Pastor Di Stacey said Mr Walker was "a very special young man".