The volume is about 10 times greater than the amount used to destroy the Alfred P. Murrah Federal Building in Oklahoma City. That blast killed 168 people on April 19, 1995.
U.S. Attorney William Wilmoth said it is unclear exactly when the chemical was removed from a bulk storage bin at Bruceton Farm Services in Bruceton Mills. The theft was reported to the sheriff's department Wednesday, he said.
The ammonium nitrate had been held in an elevated container that trucks pull under for filling. The variety stolen is normally used as a blasting agent for commercial explosive use, not as a fertilizer, Wilmoth said.
A secretary at Bruceton Farm Services said no one at the company was available to discuss the theft Friday afternoon.
But Wilmoth said access to the filling area "apparently wasn't very well secured."
"I'm not a chemist, but I understand that ammonium nitrate has at least two grades," Wilmoth said. "One is a fertilizer grade; the other is explosive grade. This was explosive grade. I am told that BFS sells this material principally to a limited number of mining companies."
FBI agents in Pittsburgh are working with the Bureau of Alcohol, Tobacco and Firearms as well as state police, Maryland State Police and other law-enforcement agencies to track the chemical down.
"At this point, all we know is the ammonium nitrate is missing," said FBI Assistant Special Agent in Charge Dennis Lormel. "Our main focus is to account for it. However, we are treating this with the utmost caution."
The FBI is offering a $10,000 reward for information leading to the arrest and prosecution of those involved in the theft.
By Vicki Smith