Mexico has so far failed fully to seal up border tunnels dug by drug smugglers, and these open tunnels pose a security risk to the United States by presenting an “open invitation” for cartels to dig new tunnels, according to officials in the United States. The United States has filled and sealed drug tunnels since 2007, after the Los Angeles Times reported that the tunnels were being left unfilled because of CBP’s budget constraints. The Mexican government said it lack the money completely to fill and seal every tunnel. Some of the tunnels are elaborate, outfitted with ventilation and rail systems to whisk contraband hundreds of yards under the border. Because of budgetary considerations, the Mexican government has been sealing only the tunnel openings – but these sealed opening are left unguarded, and the drug cartels had no trouble removing the sealing material and using the tunnels again.