Dozens of officers were deployed near Finsbury Park at around 3pm on Sunday after people tried to make their way past queues.
As temperatures rose to almost 30C (86F), large groups were seen crowded together outside to see headline sets from Minaj and Lil Baby.
Footage on social media appeared to show people jumping over gates to make their way into the event through packed crowds.
PEOPLE ARE JUMPING OVER THE GATES pic.twitter.com/t2nPYryBxQ
— RENALDO🕊 (@VegeaTredici) July 10, 2022
One person said on Twitter: “
I’m genuinely starting to get worried for Nicki and people’s safety … more people keep piling up and it’s very hot out there.”
Another wrote: “Having only the smallest opening at the singular entrance to Finsbury Park, with no regulated flow of pedestrian traffic. People being trampled and forced to climb tall gates.”
Wireless Festival warned people of fake tickets and scammers, as it issued a statement on social media saying the event was sold out.
A Metropolitan Police statement read: “A small number of people tried to get through an entrance to Wireless Festival while others were queueing.
“As a result of this, security staff put in place a brief hold on people being admitted to the event to ensure the safe flow of people into the site. This caused a large crowd to form in the area around the site.
“Officers assisted security staff with managing the crowd to keep people safe.
“We continue to work closely with the event organiser and other partners to prevent further disruption and we thank people attending for their patience, particularly in the hot weather.”
Haringey Council said two nearby roads were closed to “enable crowd safety management”.
Wireless Festival was approached for comment.