US authorities said Friday they are investigating a startling rise in bottlenose dolphin deaths along the Atlantic coast, after more than 89 creatures washed up in July.
Another 35 have already washed up so far this month, and scientists are working to find out if an infectious pathogen may be to blame since some of the dolphins appeared to have lesions in their lungs.
Fisheries experts have declared an "unusual mortality event" due to the "unexpected and significant die-off" that has spanned the coasts of New York, New Jersey, Delaware, Maryland and Virginia since early July.
"There are no unifying gross necropsy findings although several dolphins have presented with pulmonary lesions," the National Oceanic and Atmospheric Administration said in a statement.
"Preliminary testing of tissues from one dolphin indicates possible morbillivirus infection, although it is too early to say whether or not morbillivirus may be causing this event."
However, scientists say an "infectious pathogen is at the top of the list of potential causes."
Most of the dolphins were already dead when they are found. A small number have been stranded alive, only to die soon after.
Typically an average of seven dolphins wash up in Virginia in July, so the 45 animals found last month is a significant increase.
"It is an important issue," said NOAA spokeswoman Connie Barclay.
The last time morbillivirus was implicated in a mass dolphin die-off was in 1987-1988 when more than 740 bottlenose dolphins died from New Jersey to Florida.