Scientists say they're struggling to learn why dead dolphins are washing up on the U.S. East Coast in unusually high numbers this year.

Federal authorities said as of Tuesday 228 dolphin deaths had been recorded this year from New York to Virginia, CNN reported. In all of 2012, 111 deaths were recorded.

In response to the dolphin deaths, the National Oceanic and Atmospheric Administration has issued an Unusual Mortality Event declaration.

The declaration serves as official federal attention to the deaths as a possible indicator of ocean health and may give "insight into larger environmental issues, which may also have implications for human health and welfare," NOAA said in a statement on its website.

August has seen a spike in the dolphin deaths, and scientists say they're focusing on an infection as the most likely cause.

"Based on the rapid increase in strandings over the last two weeks and the geographic extent of these mortalities, an infectious pathogen is at the top of the list of potential causes for this UME, but all potential causes of these mortalities will be evaluated," NOAA said in releasing the mortality event declaration. "Work is under way to determine whether an infectious agent affecting these dolphins is present in collected tissue samples."