Three people remain in a critical condition after being injured in a crowd crush at Brixton O2 Academy in south London.One person has been arrested following the incident at a gig for Nigerian Afrobeats artist Asake, which saw five others hospitalised.The Metropolitan Police have launched an "urgent investigation" into what happened after receiving reports a large number of people were attempting to force entry to the venue.Footage shared on social media showed huge crowds building up outside the venue and clashes with police.