Counterterrorism officials are investigating the possibility that an alleged terrorist plot to attack Los Angeles-area targets on Sept. 11 or Jewish holidays was organized by members of a militant Islamic state prison gang, a top law enforcement official said today.

Federal and local officials are examining possible ties between a Pakistani national arrested in Los Angeles and a gang operating at California State Prison, Sacramento, known as Jamat Ul-Islam Is Saheeh, said George Gascon, assistant chief of the Los Angeles Police Department.

Investigators believe Hammad Riaz Samana has communicated with former or current inmates involved with the gang, Gascon said. He would not give any further details.

Samana, 21, was arrested Aug. 2 and is being held in Los Angeles, but federal officials have refused to say what charges he might face.

A source familiar with the ongoing terrorism investigation said Hammad Riaz Samana, 21, was arrested two weeks ago as part of a terrorism probe that began with the arrests of two men in Torrance suspected of robbing gas stations.

Samana's arrest developed from a terrorism investigation in which authorities found what they believe was a target list after arresting two men on suspicion of a series of gas station robberies in the South Bay. That list included three National Guard facilities, the Israeli Consulate and several synagogues.

According to Gascon, authorities believe the attacks were to be carried out on Sept. 11, the Jewish High Holidays or other dates, and warned the consulate and guard that their buildings were on the list.

"The plan was to assault, to commit terrorist acts against a variety of targets," Gascon said.

The list was found at the apartment of Levar Haney Washington, 25, of Los Angeles. Washington and Gardena resident Gregory Vernon Patterson, 21, were arrested July 5 and have pleaded not guilty to robbery charges. They have not been charged in the terrorism probe.

Cathy Viray, an FBI spokeswoman, declined to comment on the investigation by federal and local agencies because it was ongoing.

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

Investigators have briefed prison officials around California and are trying to determine whether other inmates were involved, Gascon said.

It was unclear what led authorities from Washington and Patterson to Samana.

The three men attended the same mosque in Inglewood, though they were not seen meeting as a group, according to Arshed Quazi, president of the Jamat-E-Masijidul Islam mosque.

Samana attended the mosque after arriving in Los Angeles several years ago, Quazi said. Samana is from the Karachi area of Pakistan and was studying at Santa Monica College, said Quazi, who described him as gracious and respectful toward others.

"He's such a nice kid ... I'm shocked," said Quazi, who added that Samana stayed with his family across the street from the mosque.

Quazi said Washington and Patterson attended the Jamat-E-Masijidul Islam mosque together in the last five months. Quazi said the FBI questioned him several weeks ago, asking him to identify photographs of the three men.

Patterson's attorney, Winston McKesson, said Patterson has no connection to extremist groups. A message left for Washington's public defender, Jerome Haig, was not immediately returned and Samana's lawyer could not immediately be reached for comment.

Two women who answered the door at an apartment listed for Samana across from the mosque, and who identified themselves as his relatives, declined to comment Tuesday night.

From staff and news service reports-Daily Breeze.com