There have been "numerous" arrests following mass disorder at a Halloween-themed concert featuring Stormzy and Liam Payne.
There were 12,000 people at the KISS Haunted House Party in Wembley Arena, north London.
Police ordered revellers to leave the area immediately via two Tube stations after the "significant" disorder.
It's understood a nearby McDonald's had to shut because of the chaos, according to reports.
Social media photos showed police cars lining the streets.
Officers also appeared to be placing part of a car park on lockdown.
The Met Police tweeted: "Officers are on scene at Wembley Area following significant disorder after the Kiss Haunted House event.
"Numerous arrests have been made, officers are asking people to disperse immediately to the nearby Wembley Park & Wembley Central Tube Stations."
There were no reports of any serious injuries, a spokeswoman added.
The force later confirmed: "Officers have now cleared the disorder near Wembley Arena following an event earlier on.
"Those arrested for public order offences remain in custody."
Stormzy, Sean Paul, Young T & Bugsey, Anne-Marie, Liam Payne, Jax Jones, Aitch, and Majestic were all confirmed to perform at the gig.
Organisers promised this year's event - the sixth they have organised - would be the "freakiest" yet.
A KISS Haunted House Party statement said: "The safety of event goers is of huge priority to us. We have cooperated fully with the venue and police to ensure a swift resolve to any issues this evening."
