As universities resume in-person class for the fall semester across the US, more faculty members from schools that refuse to issue mask or vaccination mandates are petitioning, protesting or even resigning over a lack of safety measures at their campuses.

Hundreds of colleges and universities in the US require their students to be vaccinated to return to campus and wear masks in classes or activities, since the Centers for Disease Control and Prevention (CDC) updated its guidelines for universal masking in indoor public places regardless of vaccination status.

Despite the CDC's recommendations, some universities, primarily in conservative states, refuse to institute mask or vaccination mandates citing state laws that prohibit such restrictions.

The US Education Department on Monday said it has initiated investigations into five states, including Iowa, Oklahoma, South Carolina, Tennessee and Utah, where universal mask mandates are prohibited in schools.

The five states have Republican governors who have argued that wearing a mask should be up to the parents and have enacted laws prohibiting or restricting mandates.

The department said those five states may be violating civil rights laws protecting students with disabilities. These students are at heightened risk of severe illness from COVID-19, and the states' prohibitions on mask mandates may restrict their access to a free appropriate public education, explained the department.

"It's simply unacceptable that state leaders are putting politics over the health and education of the students they took an oath to serve," Education Secretary Miguel Cardona said in a statement.

A group of students and faculty at Georgia State University held a demonstration on Monday to demand a mask mandate and vaccine requirement. The protest came shortly after a teacher from the university was fired after refusing to teach in-person classes where masks weren't worn.

Georgia's state university system encourages masks but doesn't allow mask or vaccine mandates at its 26 schools. Last week, a University of Georgia professor resigned in the middle of a class after a student refused to wear a mask properly.

Another professor resigned from the Georgia College and State University earlier this month after a conflict with a student over masks.

More professors have been reported to have quit over lack of stringent safety measures while the universities mandate face-to-face teaching. A professor of journalism in Tennessee and an economics professor in Pennsylvania also recently resigned after their universities denied their requests to teach remotely.

The Coalition for a Just University at Pennsylvania State University has held two protests this month to call for the school to require COVID vaccines across the 90,000-student campus.

The group organized hundreds of teachers to participate in remote instruction in the first week of the new semester as the university leaders wanted a full return to in-person instruction. Last week, the group held a second protest where about 150 faculty members rallied to demand a vaccine mandate.

With the Food and Drug Administration granting full approval to Pfizer's coronavirus vaccine last week, more colleges across the country are expected to require students to get the shots. Ohio State University is one of the schools that started implementing a vaccine requirement following the approval.

Oleg Wang, a civil engineering student at Ohio State, is a supporter of the vaccine mandate and said almost everyone around him has been vaccinated. He has been closely watching the vaccination rate at his school.

"It should be safe if the voluntary vaccination rate is high when a mandate is absent," said Wang. The vaccination rate at the Ohio State was 71 percent in July, according to the university.

The University of Utah also announced on Aug 27 that it will begin imposing a vaccine mandate after nearly 1,500 students and faculty members had signed an online petition calling for the school to mandate vaccination.

According to the organizer of the petition, the vaccination rate in Salt Lake County was 54 percent as of Aug 22. The University of Utah said the rate was about 67 percent among students.

The mandate at the university, however, applies only to students, not faculty or staff. Under state law, mask mandates still remain prohibited for higher education.

Some university administrators said their hands are tied by state laws or political pressure. The University of South Carolina had imposed a mask mandate but then rescinded it after the state's attorney general said it was a violation of state budget rules.

Georgia State University's president said in response to Monday's protest that he doesn't have the authority to impose stricter mandates under the policy of the state's university system, according to a local media report.

Education officials in some conservative states have expressed opposition to their states' prohibition on mask or vaccination mandates.

Joy Hofmeister, Oklahoma's superintendent of public instruction, said in a statement that the state's law against mask mandates "is preventing schools from fulfilling their legal duty to protect and provide all students the opportunity to learn more safely in person". The state's education department will cooperate with the federal civil rights investigation, she said.