Police investigating the murder of 17-year-old Blake Newland in Limavady, County Londonderry, have been given more time to question four males.
Mr Newland was stabbed multiple times in Woodland Walk on Friday night.
In total six males were arrested as part of the murder investigation but their ages have not been made public.
On Sunday, police were granted a further 36 hours to question four of the detainees. All six of those under arrest remain in custody.
The attack happened at about 21:35 GMT on Friday.
Three people, including Blake and a man in his 50s, were taken to hospital after police and ambulance crews were called to the scene.
On Saturday, Det Insp Mark Gibson said the Police Service of Northern Ireland (PSNI) responded to a report that a man in his 50s had been stabbed.
"Officers attended and while carrying out enquiries they located Blake who was also seriously injured with stab wounds in a nearby house."
The teenager later died in hospital.
A neighbour told BBC News NI that young people from the area had tried to help Blake, wrapping him in blankets until the emergency services arrived.
An area of grass in between houses was cordoned off by police, as was an alleyway running alongside houses.
The man in his 50s was said to be in a stable condition on Saturday.