City of London Police were asked to work with the Food Standards Agency (FSA) as part of its inquiry into the scandal. It reviewed evidence from law enforcement agencies in Europe and the UK, as well as from the FSA.
The force launched an investigation in May and said it made the arrests "during the initial stages" of the inquiry. Officers also carried out searches at businesses and homes in the UK.
Detective Chief Superintendent Oliver Shaw, from the City of London Police, said:
This is an extremely complex investigation covering a number of jurisdictions and a variety of businesses.
We are working closely with police forces, other law enforcement agencies and regulators to determine whether horsemeat being used in a range of meat products was deliberate and coordinated criminal activity.
More top news
A mother feared to have been planning to travel to Syria with her four children has been charged with child abduction.
Dimitri Diatchenko was sentenced to 60 days community service after eating the animal and sending his ex graphic photos of what he did.
The starving toddler has been taken into care following the incident in Chile - but it is thought the dog may well have saved his life.