The new worry comes from the man accused of masterminding last year's terrorist bombing in Bali that killed more than 200 people and last summer's Jakarta hotel blast that left another 12 people dead.
Riduan Isamuddin, better known simply as "Hambali," has been in the hands of U.S. intelligence agents since his arrest in Thailand last August, and he's been singing.
According to interrogation reports seen by CBS News, Hambali was implementing plans to cause far more deaths using biological weapons, most likely Anthrax.
Hambali, as al Qaeda's main connection in the Far East, was apparently trying to open an Al Qaeda bio-weapons branch plant.
According to the interrogation documents, Hambali told his U.S. interrogators he had been "working on an Al Qaeda Anthrax program in Kandahar," Afghanistan.
There he worked with a man named Yazid Sufaat, a fellow member of the al Qaeda affiliated terror group Jemaah Islamiyah. Sufaat had received a degree in chemistry and laboratory science from California State University in Sacramento.
But in October 2001, when things became too hot during the U.S. bombing campaign of Afghanistan, Hambali and Sufaat fled to safety in neighboring Pakistan. There again according to the interrogation reports, the two men discussed "continuing the anthrax program in Indonesia".
In fact the men did return to the Far East and Yazid Sufaat was arrested as he tried to enter his native Malaysia.
The U.S. has asked for his extradition on another terror connection -- that he hosted two of the 9/11 hijackers when they passed through Malaysia before the attacks. Malaysia has so far refused.
While intelligence agents are confident of the intent of the Anthrax terror program, they also say it's been stymied because the terrorists haven't managed to obtain the sort of Anthrax strain that can be easily spread. Although they remain concerned that somewhere in the region they're still trying.