Did someone mix up April Fool's Day and Halloween?
On Wednesday a government employee on a run in the town of Quantico discovered a leaflet bearing the ISIS flag and Arabic script reading, "We are here from Mexico and came by train."
A total of seven of these leaflets were eventually recovered by security personnel.
"While these leaflets may be a hoax, base officials are taking their discovery seriously," a Marine Corps spokesman told The Daily Beast.
The town of Quantico is located inside the Marine Corps Base Quantico, which is the site of Marine Corps headquarters. To get access to the base, one would have to pass through a security check, stating a reason for entering the base and providing identification.
The flier itself shows an inverted Islamic State flag, with Arabic script below it.
Counterterrorism experts say that even if it turns out to be an authentic flier, the line about Mexico is unreliable.
"I don't take that particularly seriously the Mexico part. There's no reason to think that they came up from Mexico," said Daveed Gartenstein-Ross, Director of the Center for the Study of Terrorist Radicalization at the Foundation for Defense of Democracies.
Conservatives have recently raised – and government officials have recently shot down -- the allegation that foreign ISIS fighters are coming across the border from Mexico. Rep. Jason Chaffetz said last month that four men with terror ties tried to cross the border earlier this month, and Rep. Duncan Hunter said that some 10 ISIS fighters had been caught trying to infiltrate the United States from Mexico. The Department of Homeland Security has denied Hunter's claim.
"One thing that has been picked up in [ISIS] chatter is that they read the same media that we do, and they have some sense of the things we fear… it's more indicative of the communicative act, that they're trying to cause fear, rather than that they're coming up through Mexico…. sending the signal that they're just outside your most precious, most guarded facilities."
On Thursday morning, some Marine Corps officers were circulating a notice about the fliers amongst themselves, warning that ISIS was growing in its reach and abilities.
The Marine Corps said that it was currently investigating, that it could not vouch for the origin or authenticity of the fliers, and that no similar leaflets have been found at other Marine Corps bases.
Security personnel from the nearby Marine Corps Base Quantico notified the town, the FBI and the nearby Naval Criminal Investigative Service. But at this the Marine Corps is not taking additional security measures as a result of the leaflets.
The Marine Corps would not say which building the leaflets were found in, nor who found them.