SAN DIEGO - Mexican authorities have discovered an unfinished cross-border tunnel that extends 31 feet into San Diego County, federal officials announced today.

The passageway, discovered yesterday morning, originates in Baja California and is located south of the intersection of Via de la Amistad and Enrico Fermi Drive and about a half-mile east of the Otay Mesa Port of Entry, according to U.S. Customs and Border Protection officials.

So far, U.S. Border Patrol agents have not discovered access to the tunnel on the U.S. side, but an investigation is continuing, authorities said.