Three inmates from a California prison have died from what appear to be COVID-19 complications while hundreds more at a federal lockup have tested positive for the virus.

State prison officials say three inmates from the California Institution for Men in San Bernardino died at outside hospitals on Wednesday and Thursday. And federal officials said 574 prisoners and 25 staff members had tested positive for COVID-19 at several Lompoc prison facilities in Santa Barbara County, northwest of Los Angeles.

Officials have been struggling to reduce the populations of overcrowded prisons, where it is diffiult to practice social distancing measures.