The company was cited for 11 breaches of the safety code.

The inspection, which began in January, was initiated under the agency's Process Safety Management Covered Chemical Facilities National Emphasis Program. PSM encompasses a detailed set of requirements and procedures employers must follow to address hazards proactively that are associated with processes and equipment that use large amounts of hazardous chemicals.

In this case, it was the use of anhydrous ammonia in the refrigeration system.

The company was charged with a wilful violation and fined $70,000 for failing to document that the emergency shutdown system for the engine room was designed to ensure that the mechanical ventilation system was activated by an ammonia leak.

The nine serious violations, with a $61,500 fine, were cited for PSM deficiencies of the relief valves and failing to provide process hazard analysis, operating procedures, testing procedures and management of change procedures.

The company was chaged with a repeat violation, with a fine of $38,500, for failing to ensure the adequate frequency of self-inspections and tests of ammonia refrigeration equipment and vessels.

A similar violation was cited in 2011.

"Process safety management prevents the unexpected release of toxic, reactive or flammable liquids and gases in processes involving highly hazardous chemicals," said Carlos Reynolds, OSHA's area director in Little Rock.

"It's vital that Pilgrim's Pride ensure safeguards are in place to protect the safety of workers at its work sites."