The migrant caravan that has so obsessed President Donald Trump and the Republican Party is still weeks away. But Border Patrol agents are already being told to ask everyone they apprehend whether they’re a part of it.

Guidance sent to US Border Patrol on Thursday from the desk of Patrol Chief Carla Provost instructed agents to look out for “known or suspected” members of the caravan whenever they catch and process someone who’s entered the US between ports of entry. (Many asylum-seekers and families cross illegally and then present themselves to Border Patrol agents. Others seek to enter the US at official border crossings, which are controlled by a separate division of Customs and Border Protection.)

The guidance, excerpts of which were obtained by Vox, was effective immediately.

It’s unlikely that any members of the caravan will be crossing anytime soon: The lead group of the caravan, which numbers about 4,000 people, is still in the southern Mexican state of Oaxaca, and at its current pace will take six weeks or longer to reach the United States.

This hasn’t stopped Trump from obsessing over it in the closing weeks of the midterm campaign — or ordering the federal government to take immediate steps against it. The Department of Defense is already sending thousands of troops to the border to prepare for the caravan’s arrival. And now — even though internal CBP documents obtained by Newsweek shows the agency believes only a small fraction of travelers will reach the US-Mexico border — Border Patrol agents are now officially patrolling for those people, just in case.

In addition to making a note in the intake forms whenever they suspect an arrestee traveled with the caravan, agents were instructed to explicitly ask everyone they process: “Were you a part of the migrant caravan during your travels from your home country prior to your illegal entry into the United States?”

They were also instructed to ask whether the arrestee had applied for asylum with the government of Mexico. The US can’t force asylum-seekers who traveled through Mexico to apply for asylum there, but the Trump administration claims that not applying for asylum in Mexico proves that Central Americans aren’t real victims of persecution.

Similar guidance was issued to Border Patrol agents when a previous caravan approached the US this spring. While some agents have continued to ask all asylum-seekers these questions, according to lawyers, one source familiar with Border Patrol discussions told Vox that the practice fizzled out after members of that caravan stopped arriving.

The guidance itself doesn’t change anything about how a migrant will be treated. But making a note of all “known or suspected” caravan travelers when they’re apprehended means that other government officials — from asylum officers trying to determine whether someone has a “credible fear” of persecution, to assistant US attorneys choosing which border-crossers to prosecute for illegal entry — will know which migrants are suspected to be part of the caravan Trump has identified as an “invasion”-level threat.

The caravan is still weeks away from the US-Mexico border

The main group of caravan travelers, which currently numbers about 4,000 people, is still in the southern Mexican state of Oaxaca. They have tried to get buses to take them to Mexico City, for further discussions with the Mexican government about their status. (Mexico has encouraged the caravan travelers to stay in Mexico and apply for asylum there; the caravan has rejected the offer for the moment.)

But the Mexican government wasn’t willing to provide buses, so the increasingly exhausted and battered caravan has continued on foot toward the Gulf of Mexico.

While the route out of Central America through Mexico has become the dominant way for people to enter the US without papers, the journey is dangerous. Migrating as a “caravan” helps mitigate these dangers: It allows migrants to travel out in the open, too visible to be easily exploited by smugglers and too large to be easily arrested by Mexican authorities.

The absence of bus transit doesn’t just slow down the caravan; it could pose serious risks. Mexican police have started targeting caravan travelers who hitch rides on freight trains for detention. The caravan appears to be heading toward the state of Veracruz. According to the Washington Post’s Nick Miroff, that puts them on routes controlled by the Zetas — the cartel that rose to prominence in Mexico early in the decade for being particularly murderous.

Now it seems the main caravan, unable to get buses to Mexico City, will head instead for Veracruz & presumably Tamaulipas after that (shortest path to USA). Those two states are graveyards, where untold numbers of migrants have disappeared over the past decade. It's Zeta country. — Nick Miroff (@NickMiroff) November 1, 2018

As Miroff notes, caravan-style travel makes it harder for groups like the Zetas to make money. Indeed, that’s one chief reason why the “safety in numbers” strategy is so appealing. So the caravan is, in a sense, about to cross into extremely hostile territory. The road to the United States is very, very long indeed.