SAN DIEGO (Border Report) — A yard used by food trucks to park at night in Tijuana is being heavily watched by members of Mexico’s National Guard and other law enforcement.

Investigators say someone was digging several suspected drug tunnels at the property.

One shaft was reportedly connected to an existing tunnel that led into the U.S.

It was discovered Tuesday evening, but authorities refuse to say what led them to the site.

They will say that the entire neighborhood is watched constantly because, in past years, five tunnels have been discovered in this same area east of the Tijuana airport, known as Colonia Otay Nueva Tijuana.

The commercial side of Otay Mesa Port of Entry is on the north side of the border from where the tunnels were being dug.

This is where trucks are inspected as they enter the U.S.

Despite attempts to clarify the situation, emails to Customs and Border Protection regarding the potential tunnel under the border crossing, remained unanswered.

The tunnel’s north exit point has yet to be made public.

Neither U.S. nor Mexican officials have said whether the tunnel was being used to get drugs or people across the border.

Coincidentally, the property in question sits next to a Mexico National Guard installation and offices of Mexican Customs.

Neither agency is being implicated nor are they suspected of any wrongdoing.