Al Qaeda Sympathizers May Pose Sleeper Cell Threat

WASHINGTON, July 13, 2005 — -- ABC News has learned that there are hundreds of people in the United States with suspected ties to al Qaeda and whom the government fears could become part of terrorist sleeper cells in this country.

British investigators say the suspected suicide bombers responsible for last week's terror attacks in London behaved like a classic sleeper cell, raising concerns that more such attacks might be possible. Since the Sept. 11, 2001, terror attacks, the U.S. government has already arrested and jailed extremists who were believed to be involved in planning attacks.

"We've had sleeper cell cases," said Homeland Secretary Michael Chertoff. "We've often arrested people or brought those cases down early in the process. If you wait until people are doing operational planning, you are waiting too long."

In March, the FBI had identified more than 1,000 people suspected of being al Qaeda sympathizers in the United States, according to documents obtained by ABC News. At any given time, government sources say, the FBI has about 300 Islamist extremists who are under investigation or surveillance.

The government is trying to develop informants in certain mosques where they suspect there are radicals and is tailing or electronically eavesdropping on suspected extremists.

For those willing to carry out attacks, there are plenty of explosives readily available.

From 2001 to 2004, more than 16,000 pounds of high explosives were stolen from construction sites and demolition companies, according to the Bureau of Alcohol, Tobacco and Firearms.

Equally as alarming, more than 60,000 pounds of blasting agents like ammonium nitrate -- the same chemical used in the Oklahoma City bombing -- were stolen, as well.

One of the explosive materials preferred by terrorists around the world is a homemade concoction called TATP. An ABC News team today bought three of the primary chemicals used to make TATP at local hardware and drug stores.