Agents found an incomplete tunnel on Dec. 17 in Nogales, Sonora, Mexico. They discovered structural shoring and digging tools in the roughly 2-ft-wide by 2-ft-tall tunnel, which terminated under a parking lot 44 ft into the U.S. side.

On Sept. 19, agents found a sophisticated 627-ft-long tunnel running 31 ft underground with a rail system, two sump pumps and solar-powered lights. It was approximately 3 ft tall and 2 ft wide. The entry point was in a residence near Jacume, Mexico, 221 ft from the corrugated landing mat border fence. Agents say the exit shaft was 15 ft and did not yet have an exit point.

The longest operational tunnel emerged Aug. 13 in San Luis, Ariz. After area law enforcement agents stopped Ivan Lopez for a traffic violation, they found 325 pounds of illegal drugs and served a search warrant on a commercial property he owned: a vacant Kentucky Fried Chicken restaurant about 200 yd from the border. The KFC, which Lopez bought in April, was also near a port of entry. Inside, agents found an opening cut through the concrete slab to the 600-ft-long, 3-ft-wide and 5-ft-tall tunnel that ran under the border fence.

Customs and Border Protection fills the tunnels with concrete after investigations are concluded. In Mexico, only the entrances are closed. Several identified tunnels have later been accessed at new entry points. Customs and Border Protection spent $8.7 million to fill border crossing tunnels since 2007, according to a 2016 report by the U.S. Dept. of Homeland Security.