Missouri prisons have seen a surge of inmate deaths connected to the coronavirus this month, prompting civil rights leaders to urge additional steps to protect prisoners and staff.

Early in the pandemic, confirmed cases were common but mostly mild among Missouri prisoners. Through August, the state reported just one inmate death. But 26 additional inmates infected with COVID-19 have died since September, most of them this month.

A state spokeswoman says it isn’t certain that COVID-19 was the primary cause of death in most cases.

All but two had serious underlying conditions such as late-stage renal failure, heart disease or cancer.