California prison officials say more than 4,200 inmates in eight prisons are taking part in a hunger strike that began Monday, the second such effort by prisoners in recent months.

Prisoners are staging the hunger strike to protest what they see as a lack of progress in their push for better treatment.

The earlier strike, which spread to prisoners in other states, was aimed at getting reforms in how inmates are designated for incarceration in segregated housing units, or SHUs, which inmate advocates say leave prisoners in isolation.

Prison officials say they have been working on reforms since May and were able to end the last hunger strike by providing wool caps in winter and equipment in SHU exercise yards, and other means.

"Though promises were made at the end of the last hunger strike, and some progress has been made, it is painfully slow for people who have lived under conditions of torture for years, and often decades in California's prison system," inmate advocate Laura Magnani, a member of the American Friends Service Committee, said in a statement.

Asked about the hunger strike at a Thursday news conference, Gov. Jerry Brown said the state is trying to deal effectively with prison gangs.

"Don't be fooled by people complaining that they need to get back in the main population if these are the very same people that are calling for people to be knifed and killed and for retaliation to take place in the streets," Brown said.

The earlier hunger strike resulted in a legislative hearing on how inmates are treated, and lawmakers heard impassioned pleas for reforms by inmate advocates, experts on incarceration and family members. The review is still under way, but corrections officials made it clear Thursday that they are pushing back on the latest hunger strike, issuing memos warning prisoners that "the department will not condone organized inmate disturbances."

The memos, distributed to all state prisoners, warned that disciplinary action may be taken against inmates who participate in the strike and that leaders of the effort could be placed in a secure housing unit.

Striking inmates have missed nine consecutive meals since Monday, officials said, though they noted that prisoners have access to food from canteens at various prisons.

The hunger strike so far is affecting inmates in Calipatria and Centinela state prisons in Imperial County, Corcoran in Kings County, Pelican Bay near Crescent City in Del Norte County, San Quentin and others.

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