OSLO—Norway’s $1.3 trillion wealth fund will probe whether companies it is invested in may be using the labor of ethnic Uyghurs and other Muslims linked to China’s internment camps in farwestern Xinjiang, the head of the fund’s ethics watchdog said. The world’s largest sovereign wealth fund, which has massive market influence because it owns 1.5 percent of the world’s listed shares across 9,100 companies, operates under ethical guidelines set by parliament. Johan H. Andresen, chair of the fund’s Council on Ethics, said the fund had begun identifying companies that it said used workers that had been held in internment camps in Xinjiang. “We are concerned that some of our companies in the fund may make use of this labor. This is possibly a widespread practice,” he said in an interview ahead of the publication of the council’s annual report on Wednesday. “If we were to make a recommendation it would …