The Education Department says it’s investigating five Republican-led states with universal mask bans, saying the policies could amount to discrimination against students with disabilities or health conditions.

The department’s office for civil rights sent letters to education chiefs in Iowa, Oklahoma, South Carolina, Tennessee, and Utah. Those states have barred schools from requiring masks among students and staff, a move that the department says could prevent some students from safely attending school.

It marks a sharp escalation in the Biden administration’s battle with Republican states that say wearing masks should be a personal choice.