Fertiliser producer J. R. Simplot and Agrium has said it is to cease making ammonium nitrate amid concerns about its misuse.

The substance was used by Timothy McVeigh to help create the bomb that devastated the Alfred P. Murrah Federal Building in Oklahoma City ten years ago and manufacturers have become increasingly wary of the potential for exploiting its explosive capacity.

The firm joins Potash as another company to back away from the agricultural-based product, with Simplot AgriBusiness president Bill Whitacre adamant that there was no alternative.

In a letter sent to its North American customers, the firm explained that the "growing climate of concern about ammonium nitrate" had speeded up the decision.

"We have participated in every industry initiative and have cooperated with federal, state, and provincial officials to protect ammonium nitrate from becoming a tool of destruction," Whitacre said.

"While we applaud these efforts, we think the best way for Simplot to prevent possible misuse of this product is to no longer make it available to the marketplace."

The leading ammonia nitrate producer, Terra Industries, has said it will continue to produce the substance.

Nitric acid, the feedstock for ammonium nitrate fertiliser, is produced using platinum group metals catalysts.