Since peaking at around 1,500 people, the so-called migrant "caravan" has dwindled under pressure from Trump and Mexican migration authorities, who vowed to separate those migrants with a right to stay in Mexico from those who did not.
"Since yesterday, some began to cross into the United States to turn themselves in from Tijuana and request asylum. We understand more of (the migrants) will do the same," said Jose Maria Garcia, director of Juventud 2000, an organization dedicated to assisting migrants.
He said more migrants, many of whom are stranded in Mexico's central states, are expected to arrive in the coming days.
"We will continue to receive them and it will be up to them if they stay in the country or leave," Garcia said.