Millions of shipping containers pass through U.S. ports every year.  The security of those containers is in question after a breach - now under investigation - at one of the country's busiest ports.

FOX News Radio's Lisa Brady reports in our ongoing series on national security:

Securing America.

It's the kind of incident that makes you wonder, "What if?"  A man got over a six-foot security fence topped with barbed wire, and onto a cargo ship at Port Newark.

(Rowe) "He climbed a fence that was in the immediate vicinity of the vessel that he later boarded, so he didn't go very far."

Still, he wasn't discovered until several hours later, when the captain found him -in the captain's cabin.

(Rowe) "And that's why we conducted an investigation, to find why this sort of thing happens."

Coast Guard spokesman Charles Rowe says there's no indication this suspect had any violent intent.  He was sent for a psychiatric exam.

But Wednesday's incident was the second recent breach for the Port Authority of New York & New Jersey, after a man whose jet ski ran out of gas swam to Kennedy Airport.

Lisa Brady, FOX News Radio.