Mexican authorities have uncovered a sophisticated underground tunnel near the U.S.-Mexico border that was equipped with lighting, ventilation and an electronic transport system, which they say may connect Tijuana to a street in San Diego.

Mexico's Attorney General's Office, known as the FGR, announced the discovery Saturday following a search warrant executed at a property in the Nueva Tijuana neighborhood of Tijuana, Baja California.

Authorities said the tunnel stretched approximately 265 meters, or about 870 feet, and reached a depth of roughly 6.3 meters, or 21 feet underground.

According to investigators, the tunnel contained operational infrastructure, including lighting and ventilation systems, as well as an electronic sliding mechanism designed to move items in both directions between Mexico and the U.S.

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The tunnel was discovered through intelligence work conducted by agents with the FGR's Criminal Investigation Agency in coordination with Mexico's Security Cabinet.

Officials said the search warrant was executed as part of an investigation into alleged violations of Mexico's firearms and explosives laws as well as drug-related offenses.

Authorities said they believe the property may have functioned as a storage, logistics and trafficking center for firearms, explosives and illicit drugs.

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Photos released by the FGR appear to show agents navigating the underground passageway, access points leading into the tunnel and evidence recovered during the operation.

Investigators said they recovered ammunition, suspected methamphetamine, suspected marijuana, cell phones and various documents from the property.

Images released by Mexican authorities also appear to show ventilation infrastructure inside the tunnel, underscoring what officials described as a sophisticated operation.

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The FGR said its investigation indicates the tunnel likely connects to a street in San Diego, though authorities have not publicly identified the location or confirmed whether the U.S. side of the tunnel has been located.

The tunnel discovery comes as U.S. authorities announced charges against four individuals accused of trafficking more than a ton of cocaine through a sophisticated cross-border tunnel stretching between Tijuana and San Diego.

According to federal prosecutors in San Diego, the tunnel extended approximately 1,933 feet, reached a depth of about 55 feet and was equipped with reinforced walls, electricity, ventilation systems and rail infrastructure.

Federal investigators said the tunnel connected Tijuana to a storefront in Otay Mesa known as "Buy 4 Less," where agents discovered a concealed exit point hidden beneath the floor of a storage room.

Authorities seized approximately 1,029 kilograms, or more than 2,269 pounds, of suspected cocaine during the investigation, an amount prosecutors estimated was worth roughly $45 million.

Homeland Security Investigations said the seizure dealt a significant blow to the Jalisco New Generation Cartel, one of Mexico's most powerful criminal organizations.

The investigation resulted in charges against four suspects accused of using the tunnel to move narcotics into the U.S.

Federal officials said the tunnel was discovered after months of surveillance that began in late 2025 and culminated in coordinated enforcement actions on May 29.

Officials described the discovery as a significant blow to criminal organizations that rely on underground smuggling routes to move narcotics and other contraband across the border.

"For these defendants, it wasn’t a light at the end of the tunnel. It was lights and sirens," U.S. Attorney Adam Gordon for the Southern District of California, said.

The evidence and property have been turned over to federal prosecutors in Baja California, who will continue the investigation.

Mexican President Claudia Sheinbaum indicated Monday that she would call for explanations regarding what U.S. and Mexican officials were doing when they died due to a car accident in Mexico.

Sheinbaum said her government would investigate the incident to ensure no laws were broken after the deaths on Sunday, adding that state governments must have authorization from Mexico’s federal government to collaborate with U.S. and other foreign entities "as established by the Constitution," according to The Associated Press.

The deadly incident, which killed two U.S. embassy personnel and two individuals with the Chihuahua State Investigation Agency (AEI), occurred after a drug-related operation in Mexico.

"It was not an operation that the security cabinet was aware of," Sheinbaum said, according to the AP. "We were not informed; it was a decision by the Chihuahua government."

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In a statement issued Sunday, César Jáuregui Moreno, the Chihuahua state attorney general, announced the deaths "of the members of the State Investigation Agency, as well as two instructor officers from the United States Embassy, ​​who died in an accident while returning from the operation to destroy clandestine laboratories in the municipality of Morelos," according to an English translation.

The attorney general indicated in another statement that there were no foreign agents involved in the operation and that it was not connected to the accident.

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"In order to avoid speculation and misunderstandings surrounding the operation that led to the discovery of a drug lab in the community of El Pinal, in the Sierra de Chihuahua, the Attorney General of the State, César Jáuregui Moreno, specified that only elements of the State Investigation Agency (AEI) and the Mexican Army participated in it," the April 20 statement said, according to an English translation.

"With the above, he rules out the intervention of foreign elements, however, he specified that instructors from the United States were in the state and in a neighboring community, but for other purposes, such as teaching in the handling of drones," the office said. "He stated that around 80 officers participated in the seizure of the drug lab, 40 of them from the AEI and another 40 from the Secretariat of National Defense (DEFENSA)."

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Jáuregui Moreno said AEI Director Pedro Román Oseguera Cervantes "met with instructors from the U.S. Embassy, ​​who were in Polanco giving a course on drone operation" and "they had a flight on Sunday morning from the city of Chihuahua and asked for assistance to travel along with the convoy in which the Director was traveling"

"They got into the vehicle at approximately two in the morning, and suffered the accident in which they lost their lives when it went off the road into one of the ravines in the area," Jáuregui Moreno said, also noting "there was never any involvement of any foreign agent in El Pinal."

He noted there "were no U.S. agents in the operation to secure the narco-lab," according to the AP.

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The outlet reported that the Mexican Security Cabinet confirmed that the army and state prosecutor's office executed a joint effort over the weekend in Chihuahua targeting drug labs in the same place, Morelos.

U.S. Ambassador to Mexico Ronald Johnson said in part of a Sunday post on X, "We are deeply saddened by the tragic loss of two U.S. Embassy personnel, the Director of Chihuahua’s State Investigation Agency (AEI), and an AEI officer in this accident."

"We honor their dedication and tireless efforts to confront one of the greatest challenges of our time. Our thoughts and prayers are with them and their loved ones. This tragedy is a solemn reminder of the risks faced by those Mexican and U.S. officials who are dedicated to protecting our communities. It strengthens our resolve to continue their mission and advance our shared commitment to security and justice, to protect our people," he added.

The U.S. State Department did not provide further comment to Fox News Digital on Tuesday.

The Associated Press contributed to this report