The president of Mexico's National Migration Institute, the government agency that controls and supervises migration, resigned Friday.

In a brief statement, the institute announced that Tonatiuh Guillén Lopez presented his resignation to President Andrés Manuel López Obrador. Guillén Lopez, who thanked the Mexican president for the opportunity to serve the country, had been commissioner of the migration agency since December.

The statement did not give a reason for the resignation.

Messages sent to Guillén Lopez by NPR were not immediately returned.

His resignation comes as Mexico is dealing with a surge of migrants, mostly from Central America, trying to reach the United States.

The migration agency has been struggling with budget cuts and increased demands. It has come under criticism from the United States for not doing more to control the surge of migrants.

The United States and Mexico on June 7 agreed to a series of actions to address the flow of migrants, including increased enforcement by Mexico of its southern border with Guatemala.

Earlier in the day, López Obrador said that his government will bolster security at his country's southern border, acknowledging that there have been lax controls there.

"We have identified 68 crossings like that, and in all of them there will be oversight," López Obrador said as cited by The Associated Press.

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