TIJUANA, Mexico, Feb. 10 (Xinhua) -- U.S. President Donald Trump's proposed wall along his country's 3,200-km southern border with Mexico is unlikely to deter migrants fleeing violence, poverty or a lack of opportunities, a Mexican immigration official and activists said.

"There is no way to stop a person who wants to migrate or to cross the border," Rodolfo Figueroa Pacheco, a representative of Mexico's National Migration Institute in the border state of Baja California, told Xinhua.

"The real solution to the migration issue lies in the countries that expel migrants," said Figueroa, referring to policies that exacerbate violence, drug trafficking and poverty in Central America and other regions.

"Our obligation is to ensure that those who are in Mexico are orderly, safe and have their rights respected," he said.

Undocumented migrants have many ways to cross borders, noted Figueroa, adding "there's the maritime route and the overland route, the use of fake, borrowed or rented documents, and there are also tunnels and ramps. That is to say it is very complicated and difficult to deter."

Mexico's geographic location has made it a springboard for migrants who are driven not just by the promise of a better life, but often by the destruction of their own way of life, as the current refugee crisis shows.

"We can't change our geography. Baja California is where it is, so our proximity to the United States turns us into a natural corridor for migration," said the official.

Fences with floodlights, sophisticated sensors and cameras lead many migrants to avoid the overland route and find an underground alternative to cross.

On a tour of the border region, a team of Xinhua reporters met Esteban, an undocumented migrant who has sneaked across the border several times.

"This sewage system is one of the best (options), as it takes you straight to San Diego in the U.S. state of California," said Esteban. "The exit is close to a shopping center. You arrive, change into clean clothes and no problem. Sometimes you go in groups or individually."

As he walked along the edge of a steep incline, some 15 meters high, Esteban explained how, at night, some migrants slid down the side on a piece of sheet metal or other material, then sneaked through the bushes below until they arrived at a drainpipe that also leads to San Diego.

"This route still exists, but there are also other ways," said Esteban.

Some of the "other ways" are dangerous, especially for women and minors, said Salome Limas, an activist who works at a migrant shelter called Casa Madre Assunta.

Shelters usually offer migrants a place to stay for up to 15 days, enough time for those who have already traveled long distances to rest and recover before attempting a potentially dangerous crossing, said Limas.

Women who decide to risk the crossing at present, she said, are mainly those who were deported from the United States, "but must go back there, where they have homes, husbands or children."

Last year, according to government figures, some 250,000 undocumented migrants crossed the border, most from Guatemala, Honduras and El Salvador. Independent groups say the number is close to 400,000.