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Two Mexican nationals were arrested in Arizona this week after a third tunnel – providing a hidden passageway underneath the U.S.-Mexico border – was found in the town of Nogales this month, U.S. Immigration and Customs Enforcement said in a statement Thursday.

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ICE agents found the 82-foot long, 8-foot deep tunnel Tuesday while carrying out a search warrant on a home in Nogales, Ariz., the statement said. About 200 pounds of meth, two pounds of white heroin, three pounds of cocaine and six-and-a-half pounds of fentanyl were also found during the raid. The two Mexican nationals -- Jovany Robledo-Delgado and Jesus Martinez Selgado – were arrested and charged with possession and conspiracy to distribute hard narcotics. They both appeared in U.S. federal court Wednesday.

(U.S. Immigration and Customs Enforcement)

(U.S. Immigration and Customs Enforcement)

The tunnel runs from the Arizona home to the entry of a sewage pipeline called the International Outfall Interceptor (IOI). The IOI transports millions of gallons of sewage water a day from the sister cities of Nogales – one in Mexico, Sonora, the other across the international boundary in Arizona – to a treatment plant in Rio Rico, Ariz., Fox 10 Phoenix reported.

Officials also found a stash that included 200 pounds of meth, two pounds of heroin, three pounds of cocaine and 6.5 pounds of fentanyl. (U.S. Immigration and Customs Enforcement)

Officials also found a stash that included 200 pounds of meth, two pounds of heroin, three pounds of cocaine and 6.5 pounds of fentanyl. (U.S. Immigration and Customs Enforcement)

Tunnels can be used by Mexican cartel members to transport narcotics across the border. Migrants also have reportedly used tunnels to try to enter the U.S. illegally, surpassing designated ports of entry.

Officials believe the tunnel had been there for at least a few months. They carried out the search warrant on the home after receiving an anonymous tip about drug smuggling through the IOI, Phoenix’s KTVK-TV reported. It was the third discovered in Nogales  during December.

On Dec. 4, U.S. Customs and Border Protection (CBP) agents and Mexican police found an incomplete tunnel under the streets during a routine sweep of a stormwater drainage system that serves the sister cities of Nogales on both sides of the border, Fox 10 reported.

It ran about 10-feet underground for about 20 feet into the U.S. from the Mexican side of the border. It was about three-feet wide and four-feet tall. Agents found its entrance in the floor of an existing drainage system tunnel – the opening blocked off by dirt and a mixture of Styrofoam and concrete. No people or drugs were found inside.

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Some 50 yards away – a second was found on Dec. 10. CBP agents apprehended four migrants after spotting them on surveillance camera attempting to cross the U.S.-Mexico border, according to Fox 10. While retracing the migrant’s journey, agents located the tunnel about 5 feet north of the International Boundary Fence. Mexican police later located the entrance to the tunnel on the other side of the fence. It stretched about 10-feet below ground.