Third border tunnel leading north from Mexico to United States found

NOGALES, Mexico -- As President Trump's battle for a border wall continues, three incidents in the past six weeks have officials questioning the need.

KPHO-TV dropped down into a tunnel system beneath the city of Nogales, showing an underground sewer that heads north towards the United States.

According to residents of the Mexican city, smugglers use the sewer system as a superhighway.

Two weeks ago, Mexico federal police discovered a drug tunnel leading into the United States.

It was the third tunnel found under Nogales since December.

RELATED: Border Patrol agents discover hidden border tunnel in south Texas

The problem is, Nogales already has a 25-foot tall, fully reinforced border wall that smugglers are just tunneling under.

"Show me a 12-foot fence and I'll show you a 14 foot ladder," Phoenix attorney Andrew Gordon said.

Gordon worked on the last border wall project when he was counsel to the Homeland Security secretary.

"The places where the fence is going to be most effective are already in place, and have been in place since I was at Homeland Security," Gordon said.

According to experts, more agents are what's actually needed. But the consulting firm paid to recruit new border patrol agents and customs officers only produced 33 new hires all last year.

"For every complex problem, there is a solution that's quick, simple and wrong," Gordon said. "Everyone can understand a fence, but it won't do anything."