The Los Angeles Times reported today from San Diego that many of the famous tunnels built by human and drug smugglers remain unfilled, allowing them, in some cases, to be used again.
The LA Times says:
Seven of the largest tunnels discovered under the U.S.-Mexico border in recent years have yet to be filled in, authorities said, raising concerns because smugglers have tried to reuse such passages before.
Among the unfilled tunnels, created to ferry people and drugs, is the longest one yet found — extending nearly half a mile from San Diego to Tijuana. Nearby, another sophisticated passageway once known as the Taj Mahal of tunnels has been sitting unfilled for 13 years, authorities say.