The Internal Security Agency said the arrests were part of a wider investigation into the illegal production and sale of explosives that was launched after Norway asked Poland to investigate people with links to confessed mass killer Anders Behring Breivik, who killed 69 people at a youth camp in July in Norway.
Poland was asked to provide information on a man who was mentioned by Breivik as a possible source of substances that could be used in the production of explosives.
The agency said the arrests were also the result of an analysis of a manifesto that Breivik had posted on the internet.
The agency said in a statement that large quantities of explosives were seized on Tuesday and Wednesday during a search of some 100 homes and houses and dozens of cars and garages across the country. The search was carried out by the agency, police, border guards and firefighters.
A few dozen people, who had obtained chemicals at a warehouse near the western city of Poznan, are suspected of using the substances to make explosives.