TAPACHULA, Mexico (AP) — Mexico has completed its deployment of 6,000 National Guard agents to help control the flow of migrants headed toward the U.S. and filled 650 immigration agency posts to regulate border crossings, the government said Friday.

The announcement by foreign minister Marcelo Ebrard comes as Mexico puts into effect a deal on irregular immigration reached with Washington to head off stiff tariffs that President Donald Trump threatened to slap on all imports from Mexico.

A Mexican official who was not authorized to speak about the deployment and requested anonymity said the National Guard agents have not been visible in large contingents because they are spread along the southern border that stretches more than 600 miles (1,000 kilometers) and as well as up Mexico's southern isthmus. They were also deployed to remote areas to target human smugglers, the official said.

The Associated Press witnessed an operation near the town of Comitán last weekend, when members of the new militarized policing force patrolled dirt roads through jungle in the dark.

The National Guard has not reappeared on the banks of the Suchiate river across from Guatemala in Ciudad Hidalgo since early in the week. Migrants continued crossing on rafts early Friday morning. National Guard agents have been spotted intermittently in southern states supporting immigration officials at highway checkpoints.

On Friday, checkpoints near Tapachula on the main highway connecting Mexico to Guatemala operated as they have been in recent weeks. Immigration officials stopped public transport vans and taxis to ask passengers for their documents while the National Guard or military police looked on.

While the bulk of the migrant traffic has been Central Americans, authorities find people from all over the world.

At a checkpoint on the outskirts of Tapachula on Friday, more than 20 migrants from Pakistan, India and Bangladesh were detained.

Last weekend, authorities found nearly 800 migrants inside four semi-trailers traveling through the Gulf coast state of Veracruz. Officials have said they want to focus efforts on disrupting migrant smuggling operations.

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Since January, Mexico has detained more than 74,000 migrants and deported over 53,000, according to the latest figures available. That is expected to rise when June numbers are released.

UNICEF executive director Henrietta Fore said in a statement following a three-day visit to Mexico that 15,500 migrant minors were registered by Mexican migration authorities between January and April, mostly from Central America's Northern Triangle countries. That was a 50% increase over the same period last year.

"Unless the root causes of these migration flows are addressed, the situation is unlikely to change," she said, citing poverty, violence, gang extortion and death threats.