MINNEAPOLIS (AP) _ A growing number of professors and staff at the University of Minnesota are calling on the school to mandate COVID-19 vaccinations this fall.

Many faculty members say they are anxious about returning to the classroom as COVID-19 cases are surging due to the delta variant of the virus. More than 500 people have signed a letter supporting a vaccine mandate.

The University of Minnesota chapter of the American Association of University Professors says there is broad frustration and deep anger among faculty about unsafe reopening policies.

The university is among a handful of colleges in the Big Ten that aren't requiring COVID-19 vaccines. The university implemented a mask mandate this week.