I can't answer this question with any authority, only opinion. The discussion of "FEMA camps" started in around 2005 when Katrina occurred. Apparently there were some camps set up by FEMA around Louisiana and neighboring states where they housed Katrina victims. Those victims were not allowed to leave for "up to five months" and were given very small stipends with which to live.
There are rumors that have been flying around since then about FEMA preparing for a larger natural disaster by setting up camps across the nation. FEMA is supposedly setting up the camps in preparation for the government imposing Martial Law, rounding up 90% of the population and putting them into these "internment" type camps. There is little CREDIBLE/FACT BASED evidence to be found online, but there are plenty of stories and websites dedicated to this idea.
My opinion is that it is HIGHLY unlikely that the US Government would do anything like this as it would not only ruin our economy, but it would put the US under an even more scrutinizing Global microscope. That said, if a natural disaster were to hit the entire country and if Martial Law was imposed, I could see the Government doing this if it became necessary. . . .