FBI Letter Warns of Fertilizer Purchases for Explosives

DENVER, Feb. 24, 2011 — -- On the same day federal authorities announced the arrest of a Saudi Arabian man in Texas on charges of attempted use of a weapon of mass destruction, ABC News today obtained a letter sent by the FBI to businesses across the country, warning them to watch out for anyone who might be planning a terrorist attack using fertilizer, chemical or pesticide-based explosives.

The FBI's Denver field office has sent a letter to farm supply stores in its region warning employees to be aware of anyone who might be acting in a way that could indicate potential terrorist activity.

"Current trends in terrorist bombings show that fertilizer-based explosives are continuing as a threat throughout the world," the letter states. "Ammonium nitrate and urea-based fertilizers pose an explosive threat if prepared and initiated properly. In addition, certain pesticides can be used to cause widespread harm to people."

FBI officials insist there is no new intelligence suggesting an imminent terrorist attack, saying the letter is a continuing effort of a nationwide program known as "Tripwire"— designed to keep a dialog open between businesses and federal, state and local law enforcement. FBI field offices around the country were told by headquarters to reach out to businesses in their divisions.

"This is our reengagement of those companies to make sure that they're still on alert and that these things still exist," said FBI spokesman Dave Joly.

Word of the warning letters comes just a day after the Wednesday arrest of 20-year-old Saudi Khalid Ali-M Aldawsari in Texas.

Federal authorities allege Aldawsari purchased chemicals and equipment necessary to build an improvised explosive device, and that he also researched potential targets including hydroelectric dams and nuclear power plants.

According to an affidavit, a chemical supplier tipped off the FBI to Aldawsari's attempted suspicious purchase of chemicals that can be used to make an explosive known as trinitrophenol, or T.N.P., or picric acid.