New Jersey State Police guarding the gates outside of the Hot 97 Summer Jam 2015 at MetLife Stadium had bottles thrown at them by people in the crowd who were trying to get inside -- some without tickets -- and they later used tear gas to try to disperse them, according to officials.

Kendrick Lamar, Chris Brown, Trey Songz and Big Sean were all scheduled to play at the event, billed as "the hottest hip hop event of the year."

State police said crowds of people tried to "illegally" force their way into the sold-out concert Sunday night and became upset when the gates were closed and blocked off by police in riot gear.

Police said crowds began climbing over fences and forcing their way through security personnel. The gates to the stadium were shut and troopers were called in to help maintain order, police said.

An armored state police vehicle began blasting a piercing loud noise to try to disperse the crowd and police later deployed tear gas.

A state police spokesman said some arrests were made, but the number of arrests wasn't immediately known.

Photos and video on Twitter and Instagram showed large crowds, trash-strewn streets and barricades overturned in the stadium's parking lot.

Images also showed police in riot gear using large military-style vehicles to try to disperse the crowds.

Concertgoers revealed to NBC 4 New York, that people who legally bought tickets that cost hundreds of dollars were still turned away and told to leave. Emmis New York, which owns the radio station Hot 97, said they'll refund tickets for those people.

"When fans realized tickets were not available at the box office, a small number of people created an unsafe environment, and for the safety of all guests, the New Jersey State Police were on scene to disperse the crowd. The gates were closed at that time. No further entry was permitted into the event," the radio station said in a statement.

It wasn't immediately clear if there were any injuries.