The celebration took place inside the school hall of Elm Park Primary School on Calbourne Avenue on March 22.
Emergency services were called to the address at around 9pm after an incident broke out inside the venue, resulting in two youths, 16 and 19, being stabbed.
Chilling footage from the evening captured party goers screaming and running from the hall, as what appears to have been a large knife was held in the air.
The Metropolitan Police have confirmed this morning (March 29) that a large group attended the private party, “some armed with weapons, and assaulted and robbed members of the public”.
There were three arrests made on March 22, including two 14-year-old girls and a 16-year-old boy on suspicion of assaulting emergency workers.
The following day, police arrested two boys aged 15 and 17 in Hornchurch on suspicion of possessing an offensive weapon.
The arrest total has now more than doubled, with twelve arrests made in connection to the incident, all between the ages of twelve and 17.
There have been no charges at this stage.
The Met have also revealed that the British Transport Police is helping with the investigation after the group is suspected to have travelled between Elm Park, Dagenham and Barking on both trains and buses.
A spokesperson for the force said: “At this time, 12 people have been arrested, aged between 12 and 17, in connection to this incident for various offences including possession of an offensive weapon and assault on an emergency services worker. There have been no charges at this time.
“We are now making an appeal to anyone with information as to the identities of any other people involved in this incident to come forward.
“The violence seen on Saturday evening has no place in our society and it will not be tolerated.
“We will work with our colleagues from the British Transport Police, our partners in Havering, Redbridge and Barking & Dagenham councils as well as the local community to ensure those responsible are held to account for their actions.”
If you believe you know anyone involved in this incident then you can report directly and anonymously via Crimestoppers at www.crimestoppers-uk.org or 0800 555 111, quoting PMP/8249/25.
People in possession of photos or videos of the incident should also get in touch via Crimestoppers, quoting the same reference.
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Footage will be reviewed and officers will get in contact.
Any victims of crime as part of this incident who are yet to come forward are encouraged to do so.
If you were a victim of crime on March 22 between 19:00hrs and midnight then please contact police either via Crimestoppers or 101 and quote OP ESTRAGON
