Mars Wrigley has been fined $14,500 (£12,000) after two factory workers fell into a vat of chocolate.
Officials said the workers - who were employed by an outside contracting firm - fell into the partially filled chocolate tank while doing maintenance work in June last year.
Emergency responders were able to free the pair by cutting a hole in the bottom of the tank, in Elizabethtown Pennsylvania, officials said
Both workers were taken to hospitals, with one carried by helicopter, but there was no indication that either had suffered injuries.
The Occupational Safety and Health Administration (OSHA) cited Mars Wrigley on 7 June 2022 saying the workers were not authorised to work in the tanks and were not trained on the proper safety procedures for the equipment.
The incident was labelled as "serious" in the report which said: “The employer did not furnish employment and a place of employment which were free from recognised hazards that were causing or likely to cause death or serious physical harm to employees.”
The OHSA added: “The employer did not ensure that the employee had the knowledge of the type and magnitude of the energy for the task.
“The host employer did not provide the outside employer with the correct energy control procedure or work authorisation permit.”
The workers fell into a batching tank - a tank used to mix ingredients - for Dove chocolate, a brand sold in the US. In the UK and elsewhere, Dove is sold as Galaxy.
A company representative told reporters last week that the safety of workers and outside contractors “is a top priority for our business”.
They said: “As always, we appreciate OSHA’s collaborative approach to working with us to conduct the after-action review.”
The Elizabethtown M&M/Mars site is run by Mars Wrigley, which produces M&Ms and several other popular sweet treats, including Snickers and Twix.
Milk chocolate is melted at around 45C before tempering, which is slightly above the recommended safe temperature for a bath. That temperature is unlikely to cause scalding unless maintained for a long period of time.
The workers were equipped with safety clothing which may have protected them from burns until the chocolate cooled around their bodies.