ANCHORAGE, Alaska (AP)­ ­­– A national environmental group on Wednesday asked federal fisheries officials to block an oil company’s plans for offshore hydraulic fracturing underneath Alaska’s Cook Inlet because of the threat to the inlet’s population of endangered beluga whales.

The Center for Biological Diversity in a letter to the National Marine Fisheries Service said fracking increases risks of spills, earthquakes and toxic pollutants to belugas, which were declared endangered in 2008.

“Offshore fracking poses a grave and imminent threat to critically endangered Cook Inlet...