Migrants, part of a caravan of thousands from Central America trying to reach the United States, leave a temporary shelter voluntarily closed by Mexican authorities for sanitary reasons, in Tijuana, Mexico on Sunday, January 5, 2019. [Photo:VCG]

A boy plays with a balloon as Mexican Federal Police officers stand guard outside a warehouse which was being used as a temporary shelter by Central American migrants wanting to reach the United States, in downtown Tijuana, Mexico, on Sunday, January 5, 2019. After a day-long standoff with Federal Police, dozens of migrants who are to be relocated finally left the warehouse which authorities ordered to be closed due to sanitary conditions. [Photo:VCG]

A migrant, part of a caravan of thousands from Central America trying to reach the United States, carries a mat while leaving a temporary shelter voluntarily, which is to be closed by Mexican authorities for sanitary reasons, in Tijuana, Mexico on Sunday, January 5, 2019. [Photo:VCG]

Migrants, part of a caravan of thousands from Central America trying to reach the United States, look on as they refuse to leave a temporary shelter voluntarily, which is to be closed by Mexican authorities for sanitary reasons, in Tijuana, Mexico on Sunday, January 5, 2019. [Photo:VCG]