Mexico's president nominated the country's director of prisons to lead the country's National Immigration Institute after its director resigned Friday.

The Associated Press reported that Tonatiuh Guillén submitted his resignation on Friday, which was swiftly followed by an announcement from President Andrés Manuel López Obrador of his replacement, Francisco Garduño.

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No reason was reportedly given for Guillén's replacement, which came days after he was named head of a new effort to slow migration from elsewhere in Central America through Mexico to the United States.

“I thank Tonatiuh very much. He helped in the beginning of this government,” López Obrador said at a press conference, according to the AP. “Now I am proposing as his substitute Francisco Garduño.”

The announcement of Guillén's resignation came the same day Mexico's government released the text of an agreement signed last week between the U.S. and Mexico, which states that the two countries will begin negotiations on plans for Mexico to share some of the burden of processing refugee claims at the southern U.S. border.

López Obrador's government has reportedly sought to get control of the flow of migrants heading north through the country since taking office months ago and recently announced plans to send the country's national guard to its southern border with Guatemala.

President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE threatened recently to impose tariffs on Mexico if the country did not substantially reduce the number of migrants heading to the southern border of the U.S.

But that threat was dropped upon Mexico and the White House reaching the agreement last week.