Roasted pork that was purchased from a Minneapolis market and resold at a street festival was the “likely initial source” of a salmonella outbreak that sickened 80 people in August, a Minnesota Department of Agriculture investigation concluded.

The food poisoning incident has already put the street festival organizer, New York Plaza Produce, out of business and prompted the city to fine the company $1,000 for violations that included the illegal slaughter of guinea pigs for food. Now, state records obtained by the Star Tribune describe how the salmonella was traced to three whole roasted pigs that New York Plaza Produce owner Nieves Riera bought from Shuang Hur BBQ on Nicollet Avenue.

An Agriculture Department investigator determined the pork probably had low levels of salmonella when Riera bought it, but the salmonella likely grew and spread through cross-contamination. The state sent New York Plaza Produce a “notice of warning” earlier this month, a typical penalty for a first violation.

Attorneys for Riera say the market should be held responsible for selling the tainted pig. Khan Huang, owner of Shuang Hur BBQ, said the pork was not intended for resale.

Carrie Rigdon, one of the investigators in the case, said meat purchased at a retail market should not be resold.

“The fact that there was further preparation and serving at the festival, and that it was a multi-hour process, it’s likely that any contamination just multiplied” and cross-contaminated rice, beans and guinea pig meat, Rigdon said.

The investigation revealed that Riera purchased two frozen guinea pigs from a Minneapolis store and a dozen guinea pigs on Aug. 8 from Gary Ash in Cedar, Minn. Ash told investigators that Riera purchases 10 to 12 guinea pigs every two or three months. Tests of the feces in the enclosures where the guinea pigs were held tested negative for salmonella, the report said.

After obtaining the animals, Riera “cut the necks of the guinea pigs, drained the blood, removed the fur with hot water and then washed the guinea pigs with cold water,” the report said.