Immigrants I don't know about, but there are many legitimate sources for steam/something that looks like smoke as part of normal operations. And with all due respect to the helicopter pilot, I think his observations were blown out of proportions. Also, if this happened a couple of days ago, it is unlikely to have been a factor in today's incident.
You are probably correct in your assumption, just reporting what I heard. Time will tell, or not.
Thank you Godzilla.