SACRAMENTO -- San Quentin State Prison says it will stop accepting inmates from 19 Northern California counties Wednesday because of fears over the swine flu.

Nearly half the 5,200 inmates in the prison north of San Francisco are being quarantined. Officials say tests show four inmates likely have the H1N1 virus, and 47 inmates are showing symptoms.

Luis Patino, a spokesman for the federal receiver who oversees prison medical care, says inmates aren't being shipped to other prisons for fear they could spread the pandemic flu. That means there's no room for new inmates to be shipped in from county jails.

He couldn't immediately say how long prison officials plan to halt acceptance of new inmates or how many inmates will be affected by the freeze.