At the time in question this journalist witnessed a group of federal police entering the Zocalo as I returned home, one was carrying a CAR-15 assault rifle.
The four people were detained but are now in the hands of immigration authorities until their identities are confirmed. There is a possibility they will be deported once their embassy has identified them.
More on this as soon as we can.
But as one has already mentioned, it is very unwise to refuse to show your documents here when asked by the authorities, as this situation shows, especially when facing a 10-round per second assault rifle.
The police have total power here, you do as they say, or you end up in jail, no second option.
For now, at least, the internationals are safe and not in the hands of the PFP.
But one interesting point here is when they were approached by the police they were doing nothing more than what every tourist here was doing in the run up to the election. The Zocalo was full of television sets playing videos of last year's riots and every international here was watching them.
I am not aware of any law, but it is possible that it is illegal to publicly show political material on election day, and in doing so, or just watching, was enough to draw attention to the police.