Sadiq Khan on Saturday led tributes to a woman who died following a crowd crush outside the O2 Academy in Brixton.
Rebecca Ikumelo, 33, was one of three people badly hurt when ticketless fans tried to get into a show by Nigerian artist Asake at the south London venue on Thursday.
The Met Police confirmed that Ms Ikumelo, from Newham, died in hospital on Saturday, while two other women, 21 and 23, remain in a critical condition.
Rebecca Ikumelo, 33, who died following a crowd crush outside an Asake concert at the O2 Academy Brixton
Chief Superintendent Colin Wingrove, policing commander for Lambeth and Southwark, urged witnesses or anyone with information to come forward.
“There were around 4,000 potential witnesses present at the time of this incident and we want to urge any members of the public with information to come forward.
“We need your information as we try to establish what happened as quickly as we can.”
The force also said footage of an officer pushing a woman from the venue’s steps has been assessed by the Directorate of Professional Standards and there was “no evidence of misconduct”.
Florence Eshalomi, Labour MP for Vauxhall, said in a statement posted to Twitter: “We need answers about exactly how this happened and safeguards against it in future.
“This will be fully investigated by Specialist Crime detectives, supported by Lambeth Council’s Licensing Unit.”
One woman who was present at the venue told the Standard that she had fallen as a crowd of people rushed in and been “kicked around like a football”.
“I was going into the concert and I was crushed from behind. The crowd was insane,” she said.
“I fell down, they were stepping on my head. I couldn’t breathe.
“There was a woman next to me in a very bad way as well. A security guard was also injured and a pregnant woman outside being resuscitated.
“I thought I’d taken my last breath, I’m still getting flashbacks.”
Asake, whose real name is Ahmed Ololade, was recently nominated for BBC Radio 1’s Sound of 2023 award – for artists breaking through in the UK.
Ahead of the gig, he urged fans not to go to the venue without a valid ticket.
The concert was the third of three sold-out dates at the 4,921-standing capacity venue and concluded a run of UK dates.
Academy Music Group, which owns and runs music venues across the UK, said in a statement: “All at O2 Academy Brixton and Academy Music Group are deeply saddened by the news of the tragic death of Rebecca Ikumelo.
“We send our heartfelt condolences to Rebecca’s family and friends, and our thoughts are with everyone affected by this devastating news at this extremely difficult time.”