Three men are still being questioned on suspicion of murder as police probe more than 200 hours of CCTV footage after two teenage boys died in Essex.
The trio, aged 19, 20 and 21, continue to be interviewed by officers following the deaths at the weekend.
Police were called to Regency Court in Brentwood at around 1.30am on Sunday and found three people had been injured.
Two teenagers later died, while the third person was treated for non-life threatening injuries.
The three being questioned were among eight people arrested on Sunday.
The 19 and 20-year-olds are from Grays, while the 21-year-old is from South Ockendon.
Essex Police said a 40-year-old man from Brentwood has been released under investigation.
Four others, a 20-year-old man from South Ockendon, and three men from Grays aged 19, 20, and 49, have been told they face no further action, the force said.
It added that police have seized more than 200 hours of CCTV footage and spoken to more than 20 people as part of the investigation.
Detective Chief Inspector Stuart Truss, who is leading the investigation, said: “Our investigation is progressing well and we are building a picture of the circumstances which led up to the boys’ death.
“We have seized more than 200 hours of CCTV footage and are now methodically going through it.”
He stressed that police believe it was an isolated incident and “there isn’t a risk to the wider public”, saying the area is safe and incidents like this are rare.
He added that a police presence will remain in the area as the investigation continues and appealed for anyone with information about what happened to come forward.
Police previously said they would await post-mortem examination results before confirming the ages, identities and the cause of death of the victims.