Six employees were injured in the blast at Cambrex' plant in Charles City, Iowa, on 26 October, which occurred in the plant's drying department, sparked off by a paddle dryer used for manufacturing a feed additive for poultry.
As a result, one man was transferred to a burns unit in Iowa with 70-80 per cent burns to his body while the five other employees were treated for smoke inhalation and released.
According to an inspection undertaken by the Occupational Safety and Health Bureau in Iowa, Cambrex committed four serious violations, it was reported in local media outlet the Globe Gazette.
Reportedly, the IOSH claims that the protective equipment provided by Cambrex to its employees did not appropriately protect against the fire and explosion hazards posed by the product being processed in the paddle dryer.
In addition, employees involved in the emergency response and clean-up process had apparently not received the appropriate training for the tasks they were being asked to undertake, which included picking up contaminated debris.
Moreover, it was found that some employees were instructed by the firm to re-enter the building in the midst of the emergency to search for victims and secure any processes still running, and the IOSH determined that the employees involved in this "emergency response and containment of an explosion and release of hazardous substance" had not been trained to the hazardous materials technician level.
Finally, the bureau said that Cambrex "did not inform representatives of outside employers of all the chemical hazards present and all the precautionary measures necessary to safely enter the areas affected by the explosion".
In the aftermath of the blast an arsenic-containing chemical dust was spread throughout the drying room and nearby areas.
Each of the first three offences have attracted a penalty of $4,500, while the last one draws in a fine of $1,875, at a total cost to Cambrex of $15,375.
The company received a citation and notification of penalty from the IOSH of 7 February and would have had 15 days in which to contest them.
It is unknown what action Cambrex took, or is intending to take to address the issues raised - the firm was unavailable for comment prior to the time of publishing.
In addition to making chemical ingredients for use in animal feed additives, the plant in question, which employs 200 workers, also makes active pharmaceutical ingredients (APIs), intermediates and fine chemicals for the pharmaceutical industry.
Cambrex also operates four other manufacturing plants, two in the US, one in Italy and one in Sweden.