Crowd trouble marred West Ham’s EFL Cup fourth-round home win over Chelsea, with police making seven arrests.
Plastic bottles, seats and coins were thrown during the Hammers’ 2-1 victory at London Stadium as hundreds of supporters clashed and riot police entered the concourse.
It is the latest outbreak of disorder at West Ham’s new ground this season.
West Ham boss Slaven Bilic called the behaviour “unacceptable”, adding: “We are totally against it as a club.”
The club says it will ban any fans involved for life.
Until Wednesday’s match, the Metropolitan Police have not deployed officers inside the stadium because the radio system emergency services use to communicate will not be operational until 2017.
This season, the Hammers’ first at the former Olympic Stadium following their move from Upton Park, 23 fans have been banned from the ground.
Four people were arrested following disorder at the Premier League match against Middlesbrough on 1 October, while there were clashes in the stands during the defeat by Watford in September.
The Metropolitan Police, who made seven arrests for alleged public order offences, described Wednesday’s incidents as “unacceptable” and said 30 people were prevented from attending the match.
It said part of its investigation will include “a leaflet handed out before the match containing homophobic contents”.
Images on social media before the game appeared to show a song sheet being distributed with homophobic lyrics aimed at Chelsea defender John Terry and striker Diego Costa.
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‘Someone will get killed there’
Bilic added: “For those kind of things to happen, especially in England, is unacceptable.”
Chelsea manager Antonio Conte said: “I don’t really like to see these situations.”
One fan at the game told BBC Radio 5 live it “was an absolute nightmare”, adding: “If they don’t close that stadium someone will get killed there.”
West Ham said in a statement they “unreservedly condemn” fans’ behaviour and will work to identify those supporters involved, while Chelsea said they were “extremely disappointed to see disturbances”.
Police commander BJ Harrington said: “There were a minority of people who attended the match that were clearly intent on being involved in confrontation and violence.
“Despite extensive work with both clubs and a large and robust policing operation, there were unacceptable incidents inside and outside the stadium, before, during and after the game.”
‘Atmosphere turned toxic’
BBC’s Richard Conway at London Stadium:
With West Ham cruising towards the quarter-finals of the EFL Cup their fans were taking great delight in taunting Chelsea’s 5000 strong support.
Then tension and vitriolic chanting turned into violence. Fans told me after the game how they and their children were pelted with coins.
The atmosphere turned toxic, with attention now focused not on the pitch but on events in the stand.
A Chelsea fan broke through a line of stewards into the area dividing supporters, balancing on the tops of seats covered in claret tarpaulin. He goaded his rivals before retreating.
Then the two sets of fans surged towards one another on the stadium concourse, which sits at the top of the lower section of the ground. It took a number of stewards, eventually backed up by riot police, to quell the standoff.
The final whistle came soon after and fans eventually left the stadium. But the damage by then had been done.
I started watching football as a kid in the mid-1980s, when fan violence was rife within the game. The end of this match made it feel like I had momentarily stepped back in time.
BBC Radio 5 live presenter Jonathan Overend, commentating on the game, said: “This has been brewing all night.
“It’s been hard to watch the match because of the flash points developing. The stewards have got a tough job here. Fans are trying to burst at each other.
“They’ve been hurling missiles at each other. It looks like plastic bottles and I’ve seen what looks like three or four plastic seats being thrown.”