SAN DIEGO (CBS) — Drug smugglers along the U.S.-Mexico border have found a crack in the nation’s defenses — but officials insist California is not at risk.

KNX 1070′s Tom Reopelle reports on a new type of border fence that is apparently forcing drug smugglers to change the way they move their cargo from Mexico to the U.S.

Law enforcement officers in Arizona recently noticed that some recently-seized bundles of marijuana were oddly shaped.

Investigators first believed the 48 pounds of marijuana wrapped in thin tubular packages had been prepared for easy transport through a tunnel.

The only problem: the bundles were completely free of dirt.

That’s when investigators realized the packages had likely been passed between the bars of the fence along the Arizona border that features concrete-filled steel tubes with an approximately 4-inch space between them — just large enough to allow packages to squeeze through.

But according to Border Patrol agent Rodolfo Zuniga, due to the sheer volume that smugglers are often transporting, that method won’t work along California’s border.

“What we’ve seen recently is smuggling through the traditional land border via ultra-light aircraft and tunnels,” said Zuniga.

Border officials said they are prepared for any new methods smugglers may attempt in order to get drugs into the U.S.