Clashes between rival supporters marred West Ham's EFL Cup fourth round win over Chelsea at the former Olympic Stadium on Wednesday night.
Skirmishes broke out towards the end of the Hammers' impressive 2-1 fourth-round win as police and stewards battled to maintain segregation behind the goal being defended by West Ham.
This derby was billed as the biggest footballing test for the London Stadium so far, on a night when basketball and track cycling competitions were also taking place on the former Olympic Park.
The capacity is capped at 57,000 and 45,957 were in attendance, along with a heavy police presence.
Chelsea sold out their allocation of 5,182 tickets and, with the Hammers 2-0 up, trouble broke out.
There had already been disturbances in the stands and outside the ground at some of West Ham's previous home matches, and a series of measures were put in place ahead of a first London derby.
The clubs appealed to supporters for the tie to pass peacefully, but the entertaining match was overshadowed.
West Ham were well in control of the tie at that point. Cheikhou Kouyate rose ahead of restored Chelsea captain John Terry to head the Hammers in front and Edimilson Fernandes struck a second three minutes after the interval.
The energetic and pacey Hammers exploited uncertainty in Chelsea's defence, with Terry making his first appearance in more than six weeks following an ankle injury.
A fifth victory from nine games at their new home saw the Hammers advance to the quarter-finals and remain in contention for silverware in their first season since leaving Upton Park.
Chelsea's only remaining cup competition this season is the FA Cup.
Joining Terry as one of seven Chelsea changes following Sunday's 4-0 win over Jose Mourinho's Manchester United was Asmir Begovic, who made his third League Cup appearance of the season in goal. Both appeared rusty.
Terry flicked over an early Willian corner, but otherwise struggled in the centre of Chelsea's back three.
And the 35-year-old was beaten to Mark Noble's cross by the on-rushing Kouyate, whose header from the penalty spot soared past Begovic.
The impressive Michail Antonio shot narrowly wide before Nathaniel Chalobah's shot from 25 yards was tipped over at the other end.
Chelsea's N'Golo Kante next opted to cross when he might have been better to shoot and Manuel Lanzini should also have done better than prod Antonio's pass across goal.
An inswinging Dimitri Payet free-kick was clawed away by Begovic, who next had to parry clear Pedro Obiang's shot from 30 yards.
Chelsea had chances, too. Michy Batshuayi had to stretch to meet Oscar's centre, firing well off target as the striker showed his lack of sharpness.
Chelsea were soon two down, despite switching the back three so Terry was on the left, Luiz in the centre and Cahill on the right.
Begovic saved well as Payet tried to turn in Antonio's cross and Kante only half cleared.
West Ham worked the ball right and Fernandes cut in on to his left foot before firing a shot through Terry's legs and into the bottom corner for his first Hammers goal.
West Ham had further chances before Conte sent on Diego Costa and Eden Hazard.
Costa tested the Hammers on numerous occasions, but Chelsea's only reply was Gary Cahill's late strike, when all the attention had switched to the unsavoury scenes behind the goal.