"When you're seeing a large number of animals stranding for an unknown reason, it's telling us there's something funky going on in the environment and in the water," National Oceanic and Atmospheric Administration Fisheries public affairs officer Maggie Mooney-Seus told ABCNews.com. "Something's not right."
In July, 91 dead dolphins washed up in New York, New Jersey, Maryland, Delaware and Virginia, figures released by NOAA indicate. In 2012, those same states had a combined dolphin death toll of nine.
The causes could include environmental issues, pollution, interaction with fishing gear and diseases, Mooney-Seus said.
"When it comes to these events, there can be a combination of factors at play," she said. "Right now we're not ruling anything out."
People attempting to come to the aid of stranded dolphins could face health risks, she said.
"Regardless of whether it's healthy, dead or sick, people need to stay away from them. These are wild animals," Mooney-Seus said. "They can bite and they can transmit diseases to human. It's always wise for people to keep a safe distance."
It's against the law to approach marine animals, she noted.