According to a spokesperson for Barclays, a group of fans without tickets tried to force their way into the Power 105.1's Powerhouse show featuring musicians including The Weeknd, Migos, French Montana and Cardi B.
After the incident, the venue shut the doors and would not allow anyone else inside, even ticketed customers.
EMS treated two people on-scene after they suffered burns in their eye.
According to witnesses, pepper spray was used on the crowd, buts it's unclear where it came from.
This video posted on social media showed the crowd rushing inside:
The Barclays Center says that "For ticket holders whose tickets were not scanned, refunds will be available at the point of purchase."