Three teenagers have been arrested on suspicion of the murder of 15-year-old Keelan Wilson in Wolverhampton, West Midlands Police said.
The three boys - aged 14, 16 and 17 - were arrested on Thursday morning and will be questioned.
A 16-year-old was also arrested last week and has been released on police bail pending further enquires.
Keelan was stabbed to death just yards from his home in the city.
He was found injured following reports of violent disorder involving a group of people in Langley Road in the Merry Hill area of Wolverhampton at about 11pm on May 29.
Detective Inspector Warren Hines, from the force’s homicide unit, said: “This is a further significant development in our investigation.
“We continue to work on a number of leads and I am extremely grateful to everyone who has provided us with information.
“The tragic death of Keelan was unnecessary and tragic and we are working round the clock to understand what happened and get answers for Keelan’s family who are being kept updated with the latest developments.”