SAN FRANCISCO (KCRA) —From fake Viagra pills to knockoff sunglasses, sports jerseys and cellphone accessories, U.S. Customs and Border Protection Supervisor Jeffrey Meleg said the battle to keep counterfeit goods from landing on U.S. soil is relentless.

"It's a cat-and-mouse game," he said. "It comes in constantly. It never stops."

Meleg led KCRA 3 on a rare tour of the CBP's postal inspection facility at San Francisco's airport.

CBP is responsible for inspecting U.S. mail arriving from abroad that is being carried by passenger planes.

"We inspect about a million a month," Meleg said.

In just one recent week, Meleg said inspectors seized packages of counterfeit sports jerseys bearing the NFL and Nike logos, boxes of video game controllers in packages labeled as Sony PlayStation and cartons of pills labeled as Viagra and Cialis.

"All counterfeit -- it's to the point now where a lot of our officers can recognize the handwriting of the counterfeiters," Meleg said.

Officers routinely uncover inferior cellphone accessories bearing the labels of Samsung or Apple, Meleg said.

Almost two-thirds of the counterfeit goods continue to come from the same point of origin, according to CBP statistics.

"If it's made in China, it can be counterfeited in China," Meleg said. "Many of these items are made in the same production facility as the genuine product. But they are made with inferior source material."

Meleg cautioned consumers that many of these counterfeit products are being sold online or by street vendors or, in some cases, even by small independent retailers.

"That is what they'll do to pad the profit margins," Meleg said. "It looks like it's legit, but it's not the same quality."

Meleg said the SFO inspection facility seizes roughly 3,000 packages a year.

But, he said, counterfeit goods are just one part of a problem that involves an increasingly dangerous trend.

"A lot of people think this is 'Breaking Bad,' like this is some high school chemistry teacher," Meleg said. "This is a fully functional facility, with an H.R. department and a Christmas Party."