The Immigration hold may well be due only to the fact that the students appear to have violated their visa by not taking enough classes. It does, however, allow LEOs to do a more thorough check on them.
After the doctors suicide attempt in Glagow and with our borders still wide open seems logical to attampt to assemble such a device.....there was also a comment from a Border Patrol that a couple of times his radiation monitor indicated but no follow up.
Megahed is a permanent legal resident and doesn’t need to be taking any classes at all to maintain his status. Mohamed is carrying a normal full time load for the summer (6 credits = two full length courses, each crammed into one of a pair of short summer sessions — 5-6 weeks each at most schools). Very few grad students would be carrying more than that.