Detectives investigating the fatal stabbing of Crouch End teenager Mahad Ali have arrested three men in connection with his death.
The 18-year-old was found stabbed by police outside a warehouse party in Coronation Road in East Acton at around 2.35am on June 29.
They gave him first aid while waiting for an ambulance, which rushed him to a central London hospital where he died at 4.33am.
A post-mortem examination carried out at Uxbridge Mortuary found the cause of death to be stab wounds to his chest and abdomen.
Police are reissuing an appeal for information, aimed directly at the "mothers, sisters and girlfriends" of the people involved.
A 41-year-old was arrested on June 29 on suspicion of murder and has been released under investigation.
A 21-year-old was also arrested on suspicion of murder on July 2 and has been released on police bail to return to a police station in early August.
Another man, aged 26 was arrested on suspicion of violent disorder and has been released under investigation.
Police believe at least 40 to 50 people were at the party which may have broken into violence on a number of occasions and have reissued an appeal, two weeks on from his death.
Mahad is believed to have had an altercation inside the venue before the fight escalated and was taken outside.
DCI Luke Marks, said: "We know there were pockets of violence that occurred in and around the venue that night - separate incidents to the one in which Mahad got stabbed - and are very keen to speak with anyone who was involved in these, as they might have very important information that could shed light on what happened to Mahad.
"It is of paramount importance that those who attended and saw the events leading up to the stabbing or the incident itself come forward to talk with us.
"I appreciate that there maybe some apprehension about approaching police, but I would ask that they do not delay in making that vital decision to speak to us.
"Mahad's family have been left completely devastated and are desperately seeking answers as to why he was set upon and what sparked the altercation.
"He suffered significant injuries and there is a strong possibility that the person or people involved in the attack would have got blood stains on their clothing.
"I would appeal to anyone who knows that a loved one attended the party, who either washed or threw away items of clothing when they returned home, to approach us. Please do not remain silent.
"If you have the slightest indication that your loved one may have been involved now is the time to say something.
"To those mothers, sisters and girlfriends shielding the person or people responsible, please do the right thing."
Any witnesses or people with information about what may have happened that night can call the Incident Room on 020 8358 0200 or via twitter on @MetCC.
You can also contact Crimestoppers anonymously on 0800 555 111.
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