Multiple shots were fired inside a northern New Jersey mall shortly before closing time Monday night, and there were no immediate reports of fatalities or injuries, a county official said.

Bergen County spokeswoman Jeanne Baratta told The Associated Press that a call went out that shots had been fired at the Garden State Plaza Mall in Paramus shortly before the facility's 9:30 p.m. closing time. She said authorities had found one bullet casing.

Hundreds of law enforcement officers converged on the mall, which was put on lockdown. New Jersey State Police landed a helicopter in the parking lot of the 200,000-square-metre facility, one of New Jersey's largest and most popular shopping malls.

Baratta said SWAT teams and police with canine units were going through the mall and working to evacuate anyone who is still in there. As of 11:30 p.m., authorities believed there were still people in the mall, she said.

Jessica Stigliano, 21, of Richfield, New Jersey, told the AP that she was sitting in the mall's food court when she saw people running and yelling "shots were fired.''

Stigliano said she also began running. She said at the time she was thinking, "Not many people run for their life, but that's what I'm doing right now.''

She did not see a shooter. "It was scary to think that you could be that close to something like that,'' Stigliano said.

A manager at the Chili's restaurant at Garden State Plaza told the AP they were on lockdown and could not leave. She said a manager at the Nordstrom department store ran over to use the phone saying there had been a shooting. She did not say if the Nordstrom manager witnessed it.

Althea Brown, 26, of Paterson told NorthJersey.com that she was in a clothing store when she saw a man walk by and then heard three shots followed by two more. She said he appeared to be wearing body armor and was wearing a helmet with the visor pulled up.

Several frightened shoppers sent tweets saying they were escorted from the mall by armed state troopers. One woman wrote that she ran from the mall "screaming.''

The mall is located in Bergen County, about 27 kilometres northwest of Manhattan.

- AP