A-list celebrities including Gloria Steinem, Jay Leno, Jesse Jackson, and Bonnie Rait have joined in on hunger strikes to protest solitary confinement in California prisons, according to The Los Angeles Times.

Solitary confinement has become a method to control prison gang violence. The group of celebrities diasgree with the practice, claiming in a letter addressed to Gov. Jerry Brown that isolation units are "extensions of the same inhumanity practiced at Abu Ghraib and Guantanamo Bay."

The letter was put together by the National Religion Campaign Against Torture, a Washington-based organization, and local supporters. There will be a demonstration on Tuesday at the Capitol.

Other famous signers include Noam Chomsky, Robert Thurman, and Peter Coyote.

The organization is working to close 13 solitary confinement units across the US. According to Executive Director Rev. Richard Killmer, isolation is a type of torture.

In response, corrections spokeswoman Deborah Hoffman suggested that solitary confinement units "serve a vital role in state prisons, keeping staff and other inmates safe from the same violent gangs leading the hunger strike and terrorizing communities across California."

Singer Bonnie Raitt, who once performed at a prison in San Quentin, credited interactions with wardens and prisoners as having a "profound impact" on her, according to spokeswoman Annie Heller-Gutwillig. Some of the other signers have visited different California prisons.

The hunger strike had garnered support about one month before it began according to Carole Travis, a lawyer representing several inmates who are suing over isolation at Pelican Bay State Prison.

Prison officials said on Monday that 385 inmates refused to eat continuously since July 8 and medical staff reported that six inmates have required treatment as a result so far, three of which needed care at outside hospitals.