LOS ANGELES - A militant Islamic prison gang may have been behind a terrorist plot to attack Los Angeles-area targets on September 11 or Jewish holidays, investigators said.

The group - known as Jamat Ul-Islam Is Saheeh, or JIS - is headed by an inmate at the California State Prison in Sacramento, law enforcement officials said. It has existed for about five years and is one of at least three Islamist groups operating in state prisons, officials said.

Federal and local investigators are examining possible ties between members of the group and Hammad Riaz Samana, a 21-year-old college student and Pakistani national who was arrested August 2 in Los Angeles, said George Gascon, assistant chief of the Los Angeles Police Department.

Federal officials have refused to say what charges Samana might face, but Gascon said investigators believe he has communicated with former or current inmates involved with the gang. He would not elaborate.

Roderick Hickman, secretary of the California Department of Corrections and Rehabilitation, said he didn't know if JIS was active in other prisons, although officials believe there were radicalized inmates in all prisons.

"There is an attempt by various groups to radicalize things, and our intent is to work collaboratively with ... other law enforcement agencies to nip that radicalization of a religion in the bud," Hickman said.

Samana's arrest developed from a terrorism investigation in which authorities found what they believe was a target list after arresting two men suspected of robbing gas stations in Los Angeles County. The list included three California National Guard facilities, the Israeli Consulate in Los Angeles and several synagogues.

Authorities believe the attacks were to be carried out on September 11, the Jewish High Holidays or other dates. Authorities warned the consulate and National Guard that their buildings were on the list.

The list was found at the apartment of Levar Haney Washington, 25, who was arrested along with 21-year-old Gregory Vernon Patterson on July 5. They have not been charged in the terrorism probe.

Washington previously was an inmate at the prison outside Sacramento, and investigators are examining whether the suspected plot was organized by two inmates there: Peter Martinez, 36, who is serving a 40-year sentence for second-degree murder, and cell-mate Kevin James, 29.

Investigators have briefed prison officials around California and were trying to determine whether other inmates were involved, Gascon said. The FBI flew in two agents Monday to warn a gathering of the state's prison wardens of the threat of prison-based Islamist groups.

The Associated Press