The Northwest Detention Center locked down areas holding violent offenders as a precaution amid a hunger strike by detainees protesting their treatment and calling for an end to deportations.
U.S. Immigration and Customs Enforcement said about 330 detainees refused to eat Sunday lunch.
On Saturday, ICE said 750 wouldn't eat.
Meanwhile, immigrant-rights activists say a group of more than 20 detainees had been segregated in a small room.
They believe it's retaliation for leading the strike that started Friday.
Attorney Sandy Restrepo says the wife of a detainee talked with her husband Sunday.
That detainee said he and others were confined to one cell without bathroom breaks and couldn't move around.
ICE spokesman Andrew Munoz says he couldn't immediately comment on those reports.
The center houses nearly 1,300 people being investigated for possible deportation.