MEXICO CITY — Mexico is studying a change in the way it handles migrants who have been overwhelming its facilities near the border with Guatemala, and may try to keep more of them in newly constructed voluntary shelters rather than in detention facilities.

Tonatiuh Guillén, director of the National Immigration Institute, told The Associated Press this week that migrants requesting asylum or certain other visas would be free to come and go from the shelters. He said the first such shelter would be built in Chiapas near the southern border.

Guillén said officials are looking at a 37-acre property in Tapachula. “If everything goes well, in the second half of the year we would begin design and hopefully construction of the new facility that is more like a shelter and not confinement, coexistence and not control,” he said.

Mexico has been overwhelmed in recent months by the flow of U.S.-bound migrants, especially Central American families with children, many of whom have travelled in caravans.

President Andrés Manuel López Obrador has insisted that his main strategy to deal with migration is to improve conditions in migrants’ countries of origin so they don’t feel compelled to leave.

However, detentions and deportations in Mexico are up 150 percent so far this year.

Mexico’s efforts did not appear to immediately appease President Trump, who unleashed a broadside on Twitter on Tuesday.

Trump wrote that he was “very disappointed that Mexico is doing virtually nothing to stop illegal immigrants from coming to our Southern Border” and added that “Mexico is wrong and I will soon be giving a response!”

It was not clear what precisely triggered Trump’s tweet. White House officials said no announcement was scheduled.

Guillén did not provide many details for the plan that is still being developed. But he said the idea is to reduce the number of immigrant detention centers – there are now more than 50 – and reserve them for migrants who are awaiting deportation.

Other migrants, such as those requesting asylum or holding regional permits to work or travel in southern Mexico, would have access to the new shelters.

“This proposal speaks to the crisis in Mexico’s immigration system,” said Abbdel Camargo, a researcher at the College of the Southern Border. He said that while details are unclear, he worries that the shelters could become recruitment centers for workers rather than humanitarian shelters for families.

Camargo said the idea appeared to formalize what authorities had already done in moving migrants from the detention center in Tapachula to a fairground, which did not have adequate facilities for them.

“This government needs to urgently move from words to deeds,” said Ana Saiz, director of Sin Fronteras, a non-government organization that along with two other groups denounced detention conditions in a report to Mexico’s Senate.

Saiz said that days after that report, the government closed five small immigration detention centers, including one where abuses had been reported.

Guillén said the immigration agency had fired some 600 employees for reasons including “inadequate conduct, signs of corruption, others for (poor) performance, others for not passing confidence controls.”

But Saiz still has doubts. “There’s a lot of talk about looking for alternatives, but the detention centers are full, the massive operations continue. They separate families and even a child lost her life,” she said, referring to a 10-year-old Guatemalan girl who died last week after apparently falling from a bunk at a Mexico City detention center. The death is under investigation.

The government has denied separating families, but admits it is overwhelmed.

“The Institute does not have infrastructure for families,” Guillén said. “The (detention centers) have a very severe control model and from the perspective of children, it’s completely inappropriate.” But he said the kids are there because the government decided to keep them with their parents.

The National Human Rights Commission recently denounced confinement conditions and the lack of accurate counts of who was held at the Tapachula facility.

Guillén said the change in approach is needed urgently. But it will take time to build the shelter facilities and the U.S. is entering another election cycle where the threat of harsher measures against migrants could increase.

“This is a transition period,” Guillén said. “I hope that these flows are a stage, a circumstance, a situation and that we find a way to ease the number and improve the (migrants’) treatment quickly.”