The News Journal reports that more details by the agencies will be made available on Thursday.
"A vessel of any size can harm a whale, smaller vessels tend to be propeller strikes and larger vessels appear to be blunt trauma, so it could be a vessel of any size", says NOAA Fisheries large whale recovery coordinator Greg Silber.
The investigation will focus on possible common threads like toxins and illness, prey movement that could bring whales into shipping lanes, or other factors, officials said.
An "unusual mortality event" is a term introduced by lawmakers in the Marine Mammal Protection Act to describe an "unexpected" stranding event that is generated by a "significant" die-off of any marine animals, and which require immediate action. Data collection, analysis, and interpretation may take months, or even years.
A newborn humpback whale weights around one ton and measures about 15 feet long.
A dead humpback whale beached on Block Island, R.I., in March 2016.
Out of the 41 dead humpbacks, scientists have conducted necropsies on 20 of them.
"Most large whales, when they're feeding, they're engaged in feeding and probably relatively oblivious to things around them, including large ships coming towards them", Silber said. The last was in 2006, when the region saw 23 humpback whale mortalities.
"They're seeing these animals washing up with no apparent external injuries so that's the question and that's why it's a UME because no one has answers yet", says Schoelkopf. In some cases, it can lead them to beaches instead of deep waters.
Last fall, humpbacks along the Atlantic coast from the Caribbean to Canada were removed from the federal endangered species list.
Thurman said that one of the recent dead whales was found at the Port of Wilmington entangled in fishing gear, she said. "The other two whales from 2017 could not be examined thoroughly due to the level of decomposition and the logistical challenges surround their locations".