Two sophisticated drug-smuggling tunnels outfitted with lighting and ventilation systems have been discovered along the US-Mexico border.
Both tunnels were at least 150 yards long. One, found on Wednesday by the Mexican army, began under a bathroom sink inside a warehouse in Tijuana but was unfinished and did not cross the border into San Diego.
The other was completed and discovered on Saturday in a vacant shop in the south-western Arizona city of San Luis.
It showed a level of sophistication not typically associated with other crude smuggling passageways that tie into storm drains in the state.
Douglas Coleman, special agent in charge of the Phoenix division of the Drug Enforcement Administration, said: "When you see what is there and the way they designed it, it wasn't something that your average miner could put together.
"You would need someone with some engineering expertise to put something together like this."
As US authorities heighten enforcement on land, tunnels have become an increasingly common way to smuggle loads of heroin, marijuana and other drugs into the country. More than 70 passages have been found on the border since October 2008, surpassing the number of discoveries in the previous six years.
The latest Arizona tunnel was discovered after state police pulled over a man who had 39 pounds of methamphetamine in his vehicle and he mentioned the shop.
The tunnel was found beneath a water tank in a storage room and stretched across the border to an ice-plant business in the Mexican city of San Luis Rio Colorado. It was reinforced with four-by-six beams and lined with plywood. Investigators believe the tunnel was not in operation for long because there was little wear on its floor, and 55-gallon drums containing extracted dirt had not been removed from the property.
Mr Coleman said investigators cannot yet say for sure if the tunnel, estimated to cost 1.5 million US dollars (£970,000) to build, was operated by the powerful Sinaloa cartel. Authorities suspect cartel involvement because the group from Sinaloa controls smuggling routes into Arizona.