Six people aboard a medical transport plane that went missing off the coast of Massachusetts are presumed to be dead, the aircraft’s operator said.

The Gulfstream G100 lost contact with air traffic control in the early hours of Saturday and the US coast guard ended its search for survivors on Sunday evening in the waters off Nantucket island.

Latitude Air Ambulance, the Canadian company that operated the flight, said soon afterwards that all six people on board were presumed dead.

“We must now face the heartbreaking reality that the four members of our Latitude team, our patient and the patient’s family escort, who were aboard Heartbeat 104, are presumed to have died,” the company said in a statement. “Our thoughts are first and foremost with their families, loved ones, friends, and colleagues.”

The company’s president described it as “an unimaginable loss for our Latitude family and for everyone who loved the six people aboard Heartbeat 104”.

“Our focus now is on supporting their families, supporting our people and assisting the authorities,” Peter Byl said.

There were four Canadians and two Bermudians on board.

Canada’s transport minister, Steven MacKinnon, said Transport Canada was working with authorities on the search and rescue effort.

Clarence Togeretz, Latitude’s director of flight operations, told CBC News that two pilots and two medical staff, all Canadian, had flown to Bermuda to collect a patient and a relative.

The jet left Bermuda’s LF Wade International Airport at 11.40pm local time on Friday, according to FlightAware flight data, and was due to land at Boston’s Logan International Airport at 1.30am EDT. The Federal Aviation Administration lost contact with it just after 1am.

Authorities found a debris field on Saturday evening, which was confirmed to be from the aircraft.

FlightAware’s tracker showed the plane dropped sharply from about 7,300m to 3,300m before its communications went dark.

Air traffic control audio posted by LiveATC captured the flight’s final exchanges.

“Roger, you said you’re coming in blind. Is that what you said?” a controller asked the pilot, whose reply was difficult to hear on the recording.

The Boston Globe reported that the controller then said: “You’re coming in a little weak, so I didn’t hear what your response was, if you were declaring an emergency or not.” The controller later confirmed the pilot had declared an emergency.

Just after 1am EDT, an area fire dispatcher asked emergency crews to prepare to meet a plane with an “electrical issue”, the BBC reported. The dispatcher later said “the aircraft has lost radio and radar”.

The National Transportation Safety Board said on Saturday morning it was gathering information and had no further update.

Latitude said that it would continue to cooperate with authorities during ongoing recovery efforts and investigations.

“Determining the circumstances and cause of an aviation accident is a careful and methodical process, and we will not speculate about what occurred,” the company said.