LONDON (Reuters) - Snarling football supporters pelted each other with ripped-up seats and coins at West Ham United's game with Chelsea on Wednesday, in the very stadium where peaceful athletics fans cheered Britain's Olympic heroes four years ago.
The eruption of hooliganism, a phenomenon the English game hoped it had consigned to history, has worried the Football Association enough to launch an investigation. It will ask whether the scenes reflect a problem with the former Olympic stadium itself or are indicative of a wider malaise.
The trouble was not on the scale of the violence that scarred English football in the last century, but its location is particularly sensitive for a sport keen to brand itself as forward-thinking and open to the whole family.
After years of negotiation, West Ham finally moved into the £701 million (572.20 million pound) stadium at the start of the season, leaving their traditional home, the Boleyn Ground, after 112 years.
Their sign-off game last May had also been marked by violence, when Manchester United's team bus was pelted by missiles outside the stadium, but the scenes were largely dismissed as stemming from the emotion of the occasion.
While most supporters welcomed the move to the 60,000-seat stadium, a minority remained unhappy at what they saw as a sanitised new environment far removed from their traditional home three miles down the road.
Sporadic violence has also broken out at home games against Watford, Middlesbrough and Sunderland this season, sometimes caused by arguments among West Ham's own supporters over standing at the all-seater stadium, a contentious issue at many grounds.
Segregation of rival supporters lies at the heart of the problem. Former West Ham player Tony Gale is among those suggesting that a ground built with wide gangways for 80,000 athletics fans cannot safely be adapted to keep warring football fans apart.
"The fans were very close to each other. The ground is making it easier for those who want to make trouble to do so," he said on Sky Sports. "It's going to take a helluva lot of money to police that place because it is so so big."
The situation has been complicated by the fact that West Ham, which pays £2.5 million per season rent, does not own the stadium, which remains the property of the London Legacy Development Corporation and Newham council.
As anchor tenants, West Ham is not in charge of security. That is handled by London Stadium 185, the company in charge of stewarding.
The club has complained that too few stewards were employed at earlier games. London Stadium 185 said around 1,000 were on duty on Wednesday, more than double the level recommended for Premier League games.
The stadium has also been hit by radio problems, with the system used by police to communicate not due to be fully operational until February, 2017.
That led to a refusal by the Metropolitan Police to deploy officers inside the stadium on health and safety grounds, although riot police were sent in at the height of Wednesday's trouble.
As the club, company and football authorities sought to come up with a strategy to prevent a repeat, one lawmaker suggested on Thursday that West Ham should play without a crowd.
"If there is a repeat of the violence, the next two or three home games for West Ham should be played behind closed doors." London and Westminster Conservative MP Mark Field, vice-chairman of the all-party parliamentary football group, told the Evening Standard.
West Ham's next home game is against Stoke City on November 5.
(Editing by Andrew Roche)