US authorities are searching for six people after a medical transport plane bound for Boston, Massachusetts, went missing early Saturday morning after losing contact with air traffic controllers.
The Gulfstream G-100 was travelling from Bermuda to Boston when communication with the aircraft was lost shortly after 01:00 local time (05:00 GMT), the Federal Aviation Administration told the BBC.
The US Coast Guard said search crews later located a debris field believed to be from the aircraft off the coast of Nantucket, a Massachusetts island.
Ships, helicopters and aircraft were deployed in the search for survivors, with operations continuing through the night. Authorities said the next of kin of all six people on board had been notified.
The passengers and crew included four Canadian nationals and two Bermudian nationals.
The aircraft departed Bermuda's L.F. Wade International Airport at 23:40 local time and was scheduled to arrive at Boston's Logan International Airport at 01:30 EDT (05:30 GMT), according to flight data from FlightAware.
The plane was operated by Latitude Air Ambulances, which provides international medical flights for patients returning home.
Clarence Togeretz, the company's director of flight operations, told CBC News that two pilots and two medical staff were on board, all of them Canadian.
He said the crew had flown to Bermuda to collect a patient and their relative, who were not Canadian.
FlightAware data showed the aircraft experienced a significant drop in altitude before communications were lost. The plane descended from about 7,300m (24,000ft) to 3,300m (11,000ft).
Radio transmissions also indicated there had been difficulties communicating between the pilot and air traffic control, according to the Boston Globe, which reviewed recordings provided by LiveATC.net.
"You're coming in blind? Is that what you said?" the air traffic controller asked the pilot.
"Are you declaring an emergency, or no?" the controller added, although the pilot's response was inaudible.
The controller later said the pilot had declared an emergency.
An area fire dispatcher had also asked emergency crews shortly after 01:00 EDT to prepare for a plane reporting an "electrical issue".
The dispatcher later said: "The aircraft has lost radio and radar."
The Coast Guard said it would provide a further update on Sunday morning local time as the search continued off Nantucket.