Otay Mesa, California (CNN) Border patrol agents have uncovered two sophisticated drug-smuggling tunnels in the San Diego area.
Authorities arrested an elderly woman as part of the investigation.
Both tunnels led from Mexico to warehouses in Otay Mesa, California.
The first was discovered Tuesday after a five-month investigation.
It is about 600 yards long and equipped with a pulley system.
Investigators arrested a 73-year-old woman suspected of running the warehouse.
The second, more sophisticated tunnel was detected Thursday with help from Mexican authorities.
The 700 yard tunnel includes a multi-level electric rail system and ventilation.
According to U.S. Immigration and Customs Enforcement, these are the sixth and seventh cross-border passageways discovered in the San Diego area in less than four years.