By JOHN HEILPRINGENEVA (AP) a¿¿ Swiss prosecutors confirmed Wednesday that a criminal investigation has been opened against one of the world's largest processors of precious metals over allegations that it laundered gold obtained through war crimes. Earlier this week, the Geneva-based campaign group TRIAL announced at a news conference it had filed a criminal complaint against Swiss refiner Argor-Heraeus, claiming the company processed three tons of gold ore between 2004 and 2005 that was obtained by an unlawful armed group through pillaging in the Democratic Republic of the Congo. The Federal Prosecutors' Office in Bern confirmed it has examined the complaint and has decided to open a formal probe against the company over "suspected money laundering in connection with a war crime and complicity in war crimes." It declined to provide more details. Argor-Heraeus, which is privately-owned, is "firmly" denying the accusations and noted that previous investigations by Swiss authorities had already cleared it of all allegations, which were first aired in a report by a panel of U.N. experts on Congo in 2005. However, the TRIAL group said "the refinery knew or should have assumed that the gold resulted from pillage, a war crime." It also said the refiner helped to finance an unlawful armed group in a brutal conflict, which under Swiss law is a crime for "aggravated laundering." At Monday's news conference, Kathi Lynn Austin, executive director of the Conflict Awareness Project, outlined how TRIAL based its complaint on research into "rebels supported by the gold pipeline" that she began when she worked as a U.N. investigator in the Congo nearly a decade ago. Congo suffered back-to-back civil wars starting in 1996 in the aftermath of the Rwanda genocide that drew in the armies of other African nations in a scramble for the country's vast mineral reserves of diamonds, gold, copper, cobalt and tungsten.