The United States Coast Guard and the Buzzards Bay Task Force searched for a possible mariner in distress off the Massachusetts coast, but suspended the efforts Thursday afternoon.
Officials said Coast Guard Sector Southeastern New England watchstanders heard a mayday call over the radio at about 8:30 p.m Wednesday.
The man's voice was mumbled, according to the Coast Guard.
A Coast Guard cutter was dispatched to an area off the coast of Buzzards Bay and Vineyard Sound after another call was received shortly afterward.
Search crews remained on scene throughout the night and sent a HC-144 plane out Thursday morning; however, after searching more than 760 square nautical miles, crews found nothing.
Authorities said it was difficult to pinpoint an exact search area because watchstanders responding to the call were unable to establish communications with the caller.
The search has been suspended pending any new developments in the investigation.