It’s become a staple of President Donald Trump’s riffs on the horrors of the US-Mexico border, something he knows so well that he doesn’t even need it scripted on a teleprompter: Human traffickers gag women with tape so they can’t breathe before packing them into vans and driving them across the border illegally.

But two weeks after Trump had started talking about tape-gagged women — when a January 17 Washington Post article had questioned the claim — a top Border Patrol official had to email agents to ask if they had “any information” that the claim was actually true.

The email, shown to Vox by a source within Border Patrol, was sent as a “request for information” by an assistant Border Patrol chief, apparently on behalf of the office of Customs and Border Protection Commissioner Kevin McAleenan (referred to internally as “C-1”). It asked agents to reply within less than two hours with “any information (in any format)” regarding claims of tape-gagged women — and even linked to the Post article “for further info.”

Vox’s source indicated that they and others in their sector hadn’t heard anything that would back up Trump’s claims, but wasn’t sure if agents in other sectors had provided information. However, no one from the Trump administration has come forward to offer evidence for the claim, either before or after the internal Border Patrol email was sent. (Customs and Border Protection did not respond to a request for comment.)

The text of the email, whose subject line was “Quick Turnaround: RFI taped-up women smuggled into the U.S.,” is as follows:

All, We require your assistance on a quick turnaround for C-1. Please forward any information that you may have (in any format) regarding claims “that traffickers tie up and silence women with tape before illegally driving them through the desert from Mexico to the United States in the backs of cars and windowless vans.” Reference the news article below for further info. https://www.washingtonpost.com/politics/2019/01/17/trumps-stories-taped-up-women-smuggled-into-us-are-divorced-reality-experts-say/?utm_term=.aa7fc9337070 We require this information to be submitted to BPHQG2 by 1200 EST. V/R, Armando Sianez — Acting Assistant Chief

US Border Patrol Headquarters

It’s not clear where Trump is getting his information — but it doesn’t appear to be through official intelligence

Donald Trump’s rhetoric about the border is built on a lie: the idea that the US-Mexico border is a lawless place where American citizens are constantly in grave danger, and where criminals are able to smuggle drugs and people without any risk of apprehension. That big picture — as Vox and the rest of the media has made clear again and again — bears very little resemblance to the truth.

But the claim about women gagged with tape and packed into vans has attracted particular attention because it’s quickly become a centerpiece of Trump’s rhetoric — according to the Post, as of Friday he’d made 10 references to it in 22 days — without anyone knowing exactly where he got it from.

Border experts have told the Post and other reporters that they’ve never heard of anything like what Trump is talking about.

But it’s extremely hard to prove that such things have never happened — especially because the president has access to classified information that experts speaking to journalists do not.

That’s where traditional fact-checking tends to run into a wall. While journalists might suspect that Trump is making things up, it’s possible that he’s just repeating something he heard in a briefing (or, less plausibly, read in an intelligence report) that wasn’t open to the public.

The internal Border Patrol email provided to Vox, however, makes that seem a lot less likely.

Requests for information to the field usually aren’t made to get information backing up particular claims — much less claims being made by the president, and much less claims the president had been making for, at that point, two weeks. The implication of the email is that — after CBP had already been asked for evidence by the Post and declined comment— high-level border officials didn’t have any evidence they could point to to prove that Trump was telling the truth.

It’s possible that Trump got his intel from another agency — such as Homeland Security Investigations, which is part of Immigration and Customs Enforcement — and that CBP simply didn’t know anything about it (which would raise its own set of questions about inter-agency intelligence-sharing).

But that is much less likely than the possibility that Trump heard something that wasn’t actual intelligence, and repeated it as truth.

As the Post points out, Trump started talking about tape gags the day after a meeting with representatives of the National Border Patrol Council, the union representing Border Patrol agents. It’s possible that the claims first came up in that meeting. (NBPC did not respond to Vox’s request for comment.) If that’s true, union officials were talking about things that the management of their agency knew nothing about.

That could mean that Border Patrol management is simply out of touch with the realities of the border.

Or it could mean that one of Trump’s favorite border riffs is a piece of thirdhand gossip that Border Patrol had to scramble to try to back up.