Mexican authorities said last week they’ve discovered a suspected smuggling tunnel east of the San Ysidro border crossing in Baja California.

The Mexican Army says the passageway in the area of Colonia Libertad is 500ft (152m) long, more than a yard (0.9m) wide and 2 and a half feet (0.76m) high.

Two suspects, one a minor, have been arrested.

The military statement Saturday offered few details about the tunnel, and it was unclear whether it was in use or where it leads.

An anonymous call about suspicious activity near the tunnel’s entrance led soldiers and municipal police to the area.

In recent years, authorities have found a number of tunnels that were used to smuggle drugs and people into the United States.