(CNN) -- Hundreds of California prisoners remain on hunger strike in protest of what they describe as their harsh treatment, though state authorities and inmate-rights advocates differed over the numbers involved.
The California Department of Corrections and Rehabilitation said in a press release Thursday that 811 inmates were involved in the protest, a sharp drop from the 4,252 hunger strikers on September 29.
Jay Donahue, a spokesman for Prisoner Hunger Strike Solidarity, admitted that the numbers have likely dropped. But he said that he does not trust that the numbers being presented accurately reflect those involved.
"Our sense is that there are still many hundreds striking, and that the (corrections department) is under-reporting the numbers," Donahue said. "I'm inclined not to trust the CDCR."
By Thursday, the action was into its 11th day. The corrections department considers an inmate on a hunger strike if they have missed nine straight meals.
Earlier this week, the Prisoner Hunger Strike Solidarity group estimated that as many as 12,000 inmates were skipping meals. Many were angry about a practice of keeping them in solitary confinement for too long, some as many as 20 years, according to group spokesman Isaac Ontiveros.
"What we are hoping for is for the CDCR to negotiate and to actually, fundamentally talk about these demands," Donahue said Thursday. "I am hoping that they can do that before any serious medical problems arise. We never hope for it to get to that."
The state corrections department reported Thursday that California State Prison-Corcoran, located about 50 miles south of Fresno, had more hunger strikers -- 361 -- than any other state facility. Next was the Salinas Valley State Prison between San Jose and San Luis Obispo,with 243 strikers. Three other state prisons -- including Pelican Bay, Calipatria and Ironwood -- also had participants.
Some 578 inmates at Pelican Bay State Prison, on California's northern border with Oregon, have stopped their hunger strike and resumed eating, according to the corrections department. That includes 4 of the 11 there who have been identified as leaders in the movement. That being said, 141 at that facility are still on a hunger strike.
Based on a preliminary investigation of a riot Tuesday at Ironwood State Prison, the state claimed that an inmate was attacked because, in part, he would not participate in the hunger strike. The inmate was treated at an outside hospital, the corrections department said Thursday.
The state claimed that it is conducting several investigations into reports that inmates have been threatened or mistreated by other inmates because they have refused to participate.
Earlier, prison officials said it would punish inmates who were not eating and leaders of the strike will be removed "from the general population and be placed in an Administrative Segregation Unit."
The prisoners have made five demands, including a change in the prison policy that makes inmates go through an interrogation process in which they have to incriminate themselves -- and identify other inmates who are involved in breaking rules -- in order to get out of solitary confinement. They are demanding an end to group lockdowns and want more privileges for those in solitary confinement, such as winter clothes and nutritious meals.
Prison officials have said that placing prisoners in segregation units, or solitary confinement, makes the facilities more safe and helps guards deal with gang violence.
Donahue called the corrections department's response to the strike "very disappointing."
"They continue to claim that they have addressed the demands of the prisoners and that they are reviewing the gang validation processes," he said. "But they've said, fundamentally, that they're not going to address long-term solitary ... and they haven't said anything about group punishment."
Dozens of advocacy groups from around the world have joined the cause, according to a list on Prisoner Hunger Strike Solidarity's website, and Donahue said the group is still getting supportive calls and e-mails daily. Among those is Amnesty International, which released a statement Tuesday "calling for urgent implementation ... of policies to improve conditions" and criticizing what it characterized as California officials' subjecting hunger strikers "to punitive measures."
"The need for reform is long overdue," the human rights advocacy group said. "Amnesty International urges that the hunger strike be brought to an end through a clear commitment by the authorities to ensure humane conditions for all prisoners and a meaningful process ... so that no prisoner is held long-term or indefinitely in extreme isolation."
The strike, which started September 26, is the second such action by prisoners this year. Another occurred in July.
"Right now we are seeing nothing but crackdowns from the CDCR," Ontiveros said earlier this week. "We are hoping that there will be some fruitful negotiations, but ironically they have threatened prisoners with more isolation."
CNN's Greg Botelho and Greg Morrison contributed to this report.