BUFFALO, NY - It was just last year that metal detectors and other security came to Buffalo's City Hall. Since then, they've been busy.

They've found literally thousands of weapons on city hall visitors -- some of them very dangerous.

"It's very concerning, we don't want to have people with brass knuckles coming in the building, we don't want people with a switch blade knife," said Buffalo Common council member Rich Fontana.

But, those are exactly the type of weapons that have been confiscated by security at the City Hall entrance. Last year, the city hired a security firm called G4S Secure Solutions to tighten up security, at one of Buffalo's busiest government buildings.

"So we can avoid an accident or an incident from happening," Fontana said.

Over the past year, nearly 400 firearms have been found on visitors. More than 4,700 knives and 723 people with pepper spray.

"Those items many times were not illegal, but they weren't allowed in the building and they were given back to the person as they left the building upon exit," Fontana said.

REPORTER: What's an example of a legal weapon that's brought to city hall, but just not allowed to go into city hall?

"Sure, a firearm you can have a pistol permit to, a concealed carry pistol permit," said Lt. Jeff Rinaldo of Buffalo Police.

But other times -- illegal weapons were found. G4S Secure Solutions says their guards confiscated 33 illegal weapons, including stun guns and metal knuckles.

REPORTER: Is that concerning to you? If you didn't have the security here that stuff would've been getting in and no one would've been noticing.

"We've said that for years we've said items are in this building that shouldn't be in this building," Fontana said.

All of the illegal weapons are turned over to Buffalo Police.

"They're held onto for a period of time and then eventually, they're destroyed, they're taken to a facility where they're properly disposed of," Rinaldo said.

Police say no charges were filed against people who brought in illegal weapons, police say in many of those instances, people were unaware that a stun gun or metal knuckles were illegal. Police remind people to know what they're bringing to city hall or any government building for that matter.