The latest on Mexico's actions to stem the flow of migrants across its territory (all times local):

2:05 p.m.

Mexico's National Migration Institute says its top official has presented his resignation to the president.

The institute said Friday in a brief statement that Tonatiuh Guillén thanked President Andrés Manuel López Obrador for the opportunity to serve the country. The agency did not say why Guillén was stepping down.

Guillén presented his resignation at a time when Mexico is trying to slow migratory flows of mostly Central Americans through its territory under pressure from the United States.

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10:30 a.m.

Mexico's President Andrés Manuel López Obrador says that officials will tighten security at 68 border crossings where controls are lax.

He made the comment in a Friday morning presser, although there was no visible increase in the number of soldiers and personnel in the border city of Tapachula near Guatemala.

Foreign Minister Marcelo Ebrard said the National Guard will be deployed on Tuesday along with 825 immigration agents and 200 officials from the country's welfare department.

The plan is part of Mexico's recent agreement with the United States to limit the flow of migrants from its southern border.

Ebrard also called on the United Nations and the international community to help Mexico with immigration control and in the fight against human trafficking.