A 980-foot tunnel found by Mexican troops beneath the United States border is likely to have been used to smuggle drugs and people into the U.S., officials said Friday.

Mexican General Alfonso Duarte announced the find, saying the entrance to the tunnel was inside a house that appeared to be under construction in the border town of Tijuana, Breitbart reported.

Ten people, including one woman who has been assisting in the digging of the tunnel for the past year, have been detained in the operation.

According to officials, the tunnel was around 1.8 meters (six feet) high and a meter (three feet) wide and had a lighting and ventilation system.

In June, U.S. officials said that more than 150 secret tunnels for smuggling people and drugs into the United States have been found since 1990.