The Washington Post’s Nick Miroff got new data from Customs and Border Protection about the growing number of migrants seeking to enter the United States from Mexico. In March, he was told, about 92,000 migrants were apprehended crossing the border — 58,000 of whom came as part of migrating families.

That latter figure is stunning. The surge in what the government calls “family units” has been a source of frustration for President Trump and probably contributed to this weekend’s ouster of Homeland Security Secretary Kirstjen Nielsen. You can see how big that spike has been in recent months on the chart below: The dark-green bars mark the number of family members who’ve been apprehended.

(Bear in mind that this is not the same as illegal border crossings. Many migrants intentionally turn themselves in to authorities at border checkpoints to seek asylum.)

How big is that recent spike? There have been only five months in the past decade when there were more apprehensions overall on the southern border than the number of family members stopped there last month. In total, the number of apprehensions is the most since before the Obama administration.

This increase in family units entering the United States is significant because they are more likely to be released into the country while awaiting hearings on their asylum claims.

Miroff also shared another piece of information from the government: There hasn’t been a significant decrease in the number of migrants apprehended at the border in the past week.

Why does that matter? Because after Trump hinted that he might close the border with Mexico, he later claimed that there was no longer any need because the Mexican government had taken a stronger hand to curtail migration from Central America.

“Mexico has been great,” Trump said Saturday. “The last four or five days, they’ve been great.”

“Mexico has been absolutely terrific for the last four days,” he said the day before. “They’re apprehending everybody. Yesterday, they apprehended 1,400 people. The day before, it was a thousand. And if they apprehend people at their southern border, where they don’t have to walk through, that’s a big home run.” Later at an event, he said that the Mexican government had “done more than they’ve ever done.”

There’s no evidence that’s the case. Last week, an official with the Mexican government denied that any procedures had been changed after Trump claimed in a tweet that Mexico was now apprehending more people at its southern border.

"I don’t know exactly what the origin of the tweet is,” Foreign Minister Marcelo Ebrard said. The government’s policies were, instead, “the same thing we’ve been doing since this government began” in December.

Data from Mexico’s government indicates that about 16,000 people from El Salvador, Guatemala and Honduras were apprehended in the country in the first two months of the year. If that constitutes a sixth of the total for the year, the number of apprehensions in the country will be a bit lower than the average number since 2012.

Perhaps there was a surge in apprehensions in Mexico in recent weeks or in March more broadly. Or perhaps Trump was convinced that closing the border would have massive detrimental effects for the economy and, instead of acknowledging that he had changed his mind, looked for a rationale that could be used to avoid the move.

“I don’t mind closing the border,” he said at an event Saturday. “I’d say, you know, a lot of these fakers back there” — pointing to members of the media — “they say, ‘He will never close the border.’ It’s too much. Well, you know, close the border.” He later added that he was “okay with it.”

Closing the border probably would have done little to stem the number of migrants arriving in the country anyway. As The Post reported last week, 90 percent of those who arrived in the United States last month entered between the border checkpoints that would have been closed. Many then turned themselves in to seek asylum.

Trump’s frustration is largely that there aren’t immediately accessible solutions to the spike in migration. Meanwhile, the spike grows taller.