A sophisticated "narcotunnel" equipped with lighting and ventilation systems was found running under the border between Arizona and Mexico by agents from the U.S. Border Patrol's Tucson sector, officials said.

The tunnel, which was found on May 5 with the assistance of Mexican authorities, started inside an abandoned building in Nogales, a border city in Mexico's Sonora state.

The tunnel is 4.5 meters (15 feet) deep and 76 meters (250 feet) long, officials said.

"This tunnel is more sophisticated than others that have been discovered recently," Border Patrol Tucson sector chief Randy Hill said in a statement.

The tunnel, which was dug out of solid rock, has electric lights, water pumps and a ventilation system, Hill said.

"This is a clear example of the dangers and of the lengths to which smugglers are willing to go to get their shipments across," Hill said.

The Border Patrol considers the tunnel-building efforts to be a sign that law enforcement operations by U.S. and Mexican authorities are reducing illegal activities and forcing smugglers to literally go underground.

Since the mid-1990s, authorities have discovered many clandestine tunnels along the border.

People traffickers and drug cartels often use clandestine tunnels to cross the vast U.S.-Mexican border, which runs 3,200 kilometers (1,988 miles).

Arizona is one of the main crossing points for illegal drugs and migrants along the U.S.-Mexico border.

Mexican army troops found a tunnel in March in Mexicali, the capital of Baja California state, that was used to move drugs and illegal immigrants under the U.S.-Mexican border.

The tunnel was built about three kilometers (1.8 miles) from a U.S. immigration control post.

In December 2008, a woman was rescued by U.S. Border Patrol agents from a clandestine tunnel that collapsed as she tried to cross from Tijuana, a border city in Baja California, into the United States illegally.

In March 2007, Mexican police found a clandestine tunnel crossing under the border between Tijuana and Otay, California.

The tunnel was under construction from the Tijuana side of the border and had penetrated three meters (about 10 feet) into U.S. territory.

Seven people were rescued from a tunnel beneath the U.S.-Mexican border after being trapped for several hours in October 2006.

All seven were trapped in the tunnel connected to the sewerage network when it collapsed near the border crossing into San Ysidro, California, across the border from Tijuana.

In 2005, Mexican police discovered a tunnel, apparently used by people traffickers, linking Mexico and the United States beneath the heavily patrolled and partially walled-off border.

The tunnel, which was located near the wall that separates Mexico and the United States, in an area of Tijuana known as Ciudad Industrial, was sealed off on both sides of the border.