Federal regulators are reviewing the operations of Beef Products Inc., following a New York Times investigation that found the company’s method of using ammonia to eliminate E. coli and Salmonella from beef trim may not work as well as has been claimed.

Exposing meat to ammonia gas raises its alkalinity, which should make it less hospitable to E. coli and Salmonella. Using this method, Beef Products was able to use fattier beef trim – which is more susceptible to contamination – for ground beef. The company’s research showed this method reduced pathogen’s to “undetectable” levels.

The U.S. Department of Agriculture (USDA) was convinced by Beef Products’ research, and in 207 exempted it from routine testing of ground beef. What’s more, Beef Products’ ground beef was also excluded from recalls, even when it was an ingredient in hamburgers found to be contaminated, because the USDA assumed it to be pathogen free.

Unfortunately, Beef Products meet has been far from pathogen free. According to The New York Times report, meat sold by Beef Products to the National School Lunch Program, has tested positive three times for E. coli and 48 times for Salmonella since 2005. In fact, the firm was temporarily banned from selling meat to the program in July – the third time in three years. However, it is still being sold to other customers.

The Times has found – and Beef Products has admitted – that less ammonia is now being used in the process. But Beef Products insists this has no bearing on the effectiveness of the method.

On learning of The New York Times’ findings, the USDA said it was revoking Beef Products’ exemption from routine testing, and reviewing its operations.