After immigrants are detained by ICE, there are probably records somewhere of who has an attorney, and who is calling family members or an attorney.
For the immigrants who aren’t calling any family or lawyers, the poorest of the poor, people with little to no connection to anyone, who may not even say which country they are from, if the administration were actually trying to kill as many disconnected immigrants as possible in secret, would society know?
For example, if the administration was composed of all types of conservative people, but 30 percent were secretly Nazis or wanted racial genocide, could there be a campaign to not just remove, but kill, immigrants, and the public doesn’t find out?
Actively, no. But part of the camps is intentional neglect like thermal insulation in the housing, pack of blankets, poor material quality, pest infested bedding, no screens to stop mosquitoes, etc. The lack of protections means increased mortality and morbidity for the captured.
Since they currently house a few thousand in different centers the likelihood of a quarter of unreported dead is unlikely but not impossible. But they definitely have a short awful future which none affected deserve.
In addition to the aspects you’ve mentioned, they also have a history of denying people necessary medications. A number of people have died as a result.