Temporary worker Vincent Smith was tipping solid chocolate into the melting vat when he slipped from a platform into the 2.5m (8ft) deep unit. Smith apparently died instantly from a blow to his head from a paddle which was mixing the chocolate, according to a spokesman for the local prosecutor's office.
The spokesman, Jason Laughlin said: "There are paddles, called agitators, that are moving inside this vat. He was hit by one of them before someone could hit the shut-off valve." Three other people were on the platform at the time of the accident.
Smith, aged 29, was in the vat for about 10 minutes before rescue crews managed to recover his body.
Investigators said the chocolate had reached a temperature of 49F (120F). The accident happened during the production of a batch of chocolate destined for Hershey's.
The facility, owned by Cocoa Services Inc., is managed and operated by Lyons and Sons.
The company melts down chocolate to send out to companies which make sweets and confectionary.
Kevin Feeley, a spokesman for Lyons & Sons, told the Philadelphia Daily News: "This was a tragic accident. According to co-workers, he literally stepped into the vat. They tried desperately to save him."
The Occupational Safety and Health Administration, part of the US Department of Labor, is investigating the accident.
In July 2002, a 19-year-old worker died after falling into a vat for mixing and melting chocolate at a plant in Hatfield Township, Montgomery County, Maryland.
In August 2006, a21-year-old man survived after spending two hours trapped in a vat of chocolate at the Debelis Corporation, Wisconsin.
Meanwhile, 51 people died in food manufacturing accidents last year, according to the United States Department of Labor Statistics’ Census of Fatal Occupational Injuries in 2007. A total of 400 people died in manufacturing accidents last year, reports the census.