The NBI says the preliminary investigation into whether a former head figure of the HOK-Elanto business cooperative received bribes amounting to one million euros is complete.
The NBI's findings, contained in documents amounting to some 16,000 pages, are now headed to the prosecutor's office.
The suspect held a leadership position at HOK-Elanto between 2006 and 2013, and stands accused of bribery and aggravated bribery charges during that period.
According to the NBI some of the allegations are related to sports team sponsorships.
HOK-Elanto is part of the S-Group cooperative, which operates grocery, restaurant, retail outlets and other services across the country, including chains like Prisma, S-Market, Sokos and Hesburger, among many others.
NBI: Case exceptionally broad
During the preliminary investigation, officials interviewed 30 individuals suspected of crimes and about 100 witnesses.
All of the people suspected of wrongdoing have denied the allegations.
The NBI's head investigator on the case, Veli Matti Räsänen, said that investigations of bribery cases in the food industry are rare.
"This case is exceptionally broad," Räsänen said.
Investigation into the HOK-Elanto case began once investigation into another bribery case involving the city of Vantaa's former mayor Jukka Peltomäki was complete, he said.
According to Räsänen, the architecture design firm Forma Futura is a common factor in the investigations.
The Vantaa-based Forma Futura was found to have bribed Peltomäki and was also discovered to have been connected to another bribery case involving the former head of Finland's largest privately-owned property rental management company, the VVO Group.