After World War I, coal was discovered in 1921, and the exploitation of this source of energy began soon after. The first coal mine was opened in 1926, with qualified and experienced workers brought from Slovenia. (There were other points of extraction in Peklenica (even earlier) and Lopatinec. World War II ended the business started by "Kraljić & Majhen Co.", which was then nationalized and managed under the name of "Međimurski ugljenokopi". In that period (1946–1972), coal extraction was significant, with total output of 4,593,961 t, in average 155,000 t each year.