Officials are formally investigating the hundreds of bottlenose dolphins on the east cost, reportedly cause by a fast-spreading infection.
According to the New York Times, 124 dolphins have washed up on the shores from New York to Virginia since July. The animals are either dead or dying; 89 dolphins were beached in July, reportedly seven times the normal amount.
Tests on dolphins have lead officials to find possible signs of morbillivirus, an infection similar to an illness that killed East Coast dolphins over a 10-month span in 1987 and 1988, the Times reports.
"There are undoubtedly more dead or sick animals at sea that have gone undetected," officials told the Times.
There were reportedly 700 dolphins stranded on shores from New Jersey to Florida due to the infection in the last deadly outbreak, but there is another factor in the current one that is raising concerns. Reports say some dolphins had pneumonia, and researchers need weeks to find the cause.
Federal wildlife officials expressed their concern on Thursday about the numerous dolphin deaths. The agency declared the occurrence unusual, and will investigate to find the cause.
"Unusual mortality events are declared when a marine mammal die-off is judged unexpected, large and in need of immediate attention," the Times reports. "Investigators have failed to find a cause of death in roughly half the 60 mortality events declared since the first one in 1991."
Officials are not sure which dolphin populations are infected. There are hundreds of thousands of the animals living on the East Coast.
About 64 of the dolphin deaths occurred on the shores of Virginia, and 44 combined shore strandings between New York and New Jersey.
Anyone who finds a dolphin on the shore is should alert the authorities. Do not touch the animal and keep you pets away from the dolphin.