The U.S. Department of Education launched investigations Monday into five states that prohibit schools from setting universal mask mandates, setting the stage for potential enforcement actions as the Biden administration spars with Republican governors over COVID-19 precautions.

The investigations by the agency’s office for civil rights will determine whether those policies—in Iowa, Oklahoma, South Carolina, Tennessee, and Utah—threaten education access for students with disabilities and health vulnerabilities who do not feel safe attending school in person without virus mitigation strategies recommended by the Centers for Disease Control and Prevention.

“National data also show that children with some underlying medical conditions, including those with certain disabilities, are at higher risk than other children for experiencing severe illness from COVID-19,” Acting Assistant Secretary for Civil Rights Suzanne Goldberg wrote to leaders in those five states. “At the same time, extensive evidence supports the universal use of masks over the nose and mouth to reduce the risk of COVID-19 transmission.”

The targeted investigations will determine whether the states’ policies are a violation of the Americans with Disabilities Act and Section 504 of the Rehabilitation Act of 1973, under which schools are required to provide a free and adequate public education to students with disabilities.

Such investigations carry the implied threat of the suspension of federal funding, but they are often resolved through voluntary resolution agreements between the Education Department and the party being investigated before the process is complete.

The Education Department did not launch similar investigations in other states that have prohibited schools from setting universal mask requirements— Arizona, Arkansas, Florida, and Texas—because those states have suspended enforcement of their policies voluntarily or as the result of court action, but it said it would continue to monitor those areas.

Most recently, a judge in Florida ruled the state overstepped its authority by prohibiting local mask requirements there. Despite that court ruling, Florida Education Commissioner Richard Corcoran announced Monday evening that his agency had withheld the monthly school board member salaries in Alachua and Broward County, the first two districts to face state penalties for requiring masks.

“We’re going to fight to protect parent’s rights to make health care decisions for their children,” Corcoran said in a statement. “They know what is best for their children.”

States that ban school mask requirements say the decision of whether to wear a face covering should be left to individual students and their families.

“To suggest that bureaucrats in Washington should tell parents that they must force their children to wear a mask in school against their wishes is a drastic error,” South Carolina Gov. Henry McMaster, a Republican, said last week. “I think it’s wrong.”

But CDC guidance suggests it is necessary to use masks broadly to limit transmission within school buildings.

Several state school chiefs in the states targeted by the investigations said they agreed that their local school districts should have the flexibility to set mask requirements if they deem them necessary.

South Carolina Superintendent of Public Instruction Molly Spearman “has repeatedly implored the legislature to… allow local school boards to make decisions affecting the health and well-being of the students they serve,” said a statement from the state’s education department. The agency “is particularly sensitive to the law’s effect on South Carolina’s most vulnerable students and ... acutely aware of the difficult decisions many families are facing concerning a return to in-person instruction.”

South Carolina’s law is one of several that face legal challenges from families of students with disabilities.

Oklahoma state Superintendent Joy Hofmeister said her state would “fully cooperate” with federal officials and that she is “not surprised” by the investigation. The state’s law “is preventing schools from fulfilling their legal duty to protect and provide all students the opportunity to learn more safely in-person,” she said in a statement.

Utah state Superintendent Sydnee Dickson said she believed the federal Education Department had “unfairly defined Utah as a state where mask mandates cannot occur.” State law there does not allow school districts to independently require masks. Rather, county health departments can set such requirements, subject to repeal from country governments, the Salt Lake Tribune reports.

U.S. Secretary of Education Miguel Cardona has pledged to support school leaders who defy their states on mask requirements, assuring them they can backfill with federal relief aid to make up for any financial penalties they may face as a result.

He telegraphed potential civil rights investigations after President Joe Biden directed the Education Department in an Aug. 18 memo to “use all available tools to ensure that governors and other officials are providing a safe return to in-person learning for the nation’s children.”

“It’s simply unacceptable that state leaders are putting politics over the health and education of the students they took an oath to serve,” Cardona said in a statement Monday. “The Department will fight to protect every student’s right to access in-person learning safely and the rights of local educators to put in place policies that allow all students to return to the classroom full-time in-person safely this fall.”