Credit: Ron Rogers via ICE

Federal authorities announced today the discovery of two highly-sophisticated smuggling tunnels running between a San Diego industrial park and Tijuana, Mexico.

The tunnels - measuring more than 600 and 700 yards, respectively - connected to warehouses on both sides of the border, officials said.

Agents used a sledge hammer to uncover an elaborately concealed hatch to one of the tunnels. The hatch was covered with a concrete-like material and painted over to match the grey warehouse floor. Once the cover was removed, it exposed the opening to a shaft dropping nearly 70-feet straight down. From there, the tunnel connected to a commercial building south of the border in Tijuana.

U.S. Immigration and Customs Enforcement agents arrested a 73-year-old Chula Vista woman in connection with the tunnel. Gladdys Rodriguez has been charged with conspiracy to maintain a drug involved premises, officials said.

The first 600-yard tunnel was uncovered Monday after months of investigation and surveillance by ICE Homeland Security Investigations agents. That discovery led agents to find a second, highly engineered tunnel running more than 700 yards in length. That tunnel was built complete with a tiered electric rail system and a complex ventilation system.

"Here we are again, foiling cartel plans to sneak millions of dollars of illegal drugs through secret passageways that cost millions of dollars to build," U.S. Attorney Laura Duffy said in a statement. "Going underground is not a good business plan."

HSI officials said the operators of the tunnel filled the warehouse on the U.S. side with merchandise, including children's toys and televisions as an attempt to mask the smuggling enterprise with the appearance of legitimate business operations. The merchandise matches items associated with a similar tunnel discover last October.

The discoveries mark the sixth and seventh major tunnels found in the area over the past four years. Laid end-to-end, those tunnels would extend almost two miles. Since 2006, nearly 80 cross-border tunnels have been detected.