The tunnel extended about 20 feet into the United States, according to U.S. Customs and Border Protection.

U.S. Border Patrol agents and Mexican Federal police recently discovered the 124th illegal cross-border tunnel within the Tucson sector since 1990, the agency says.

Authorities found the incomplete tunnel, over three-feet-wide and four-feet-tall, running underneath the Nogales streets extending 20 feet into the U.S. on Wednesday, a CBP news release said.

The tunnel was located about 10 feet underground concealed in the floor of an existing drainage system with dirt and a Styrofoam, concrete mixture.

Authorities were conducting a bi-national tunnel sweep of the storm water drainage system serving both nations, the agency said.

Agents will monitor the site until it can be sealed with a concrete filler.


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Contact Star reporter Shaq Davis at 573-4218 or sdavis@tucson.com

On Twitter: @ShaqDavis1