BALI, Indonesia -- Investigators piecing together evidence in the Bali nightclub bombings disclosed Monday the main bomb was made of ammonium nitrate, a compound stockpiled by an Islamic extremist group allied with al-Qaida.

Though police stopped short of saying the bomb was made and planted by Jemaah Islamiyah, which has been blamed for a series of bombings in Southeast Asia in recent years, the use of ammonium nitrate reinforces suspicions the group was involved.

More than 180 people died in the Oct. 12 bombings, and a U.S. consular official said Monday the dead include seven Americans -- two whose remains have been identified and five others who are missing and presumed dead.

Meanwhile, Indonesia's moderate Muslim organizations demanded that authorities crack down against Jemaah Islamiyah and religious extremists, who they said represent a fringe minority of the country's 170 million Muslims.

The demands came amid a continued standoff in the town of Solo, in central Java, between police, who want to question Jemaah Islamiyah spiritual leader Abu Bakar Bashir, and scores of students at his Islamic boarding school.

Bashir, 64, is hospitalized with reported respiratory and heart problems, though police have said they do not believe he is ill. They have made no move to take him by force, but are deployed around the hospital and say they will wait to question him.

Bashir is not a suspect in the Bali bombings, but was arrested last week on suspicion of being behind several church bombings in Jakarta on Christmas Eve 2000 that killed 19 people, and in a plot to assassinate President Megawati Sukarnoputri.