The U.S. Coast Guard has suspended its search for six people aboard a Canadian-registered air ambulance that vanished during a nighttime flight from Bermuda to Boston.

The Gulfstream G100 was carrying four Canadian crew members and two passengers when it lost contact with authorities early Saturday while approaching the Massachusetts coast. The Coast Guard said crews searched more than 4,400 square miles using aircraft, helicopters, boats and cutters.

Search teams later located a debris field off Nantucket in waters roughly 80 to 90 feet deep. Authorities did not find any survivors.

The Federal Aviation Administration alerted the Coast Guard after losing contact with the aircraft around 2 a.m. Saturday. Air traffic control audio indicates the pilot reported electrical problems and declared an emergency shortly before the plane disappeared.

The pilot also appeared to tell controllers that the aircraft was “coming in blind.” Preliminary flight-tracking data showed the plane descending sharply from about 24,000 feet to approximately 10,000 feet.

Mary Schiavo, a former Transportation Department inspector general and aviation attorney, said the aircraft may have lost critical navigation instruments as a storm moved into its path, potentially causing the pilots to become disoriented.

Coast Guard Rear Adm. Matthew Lake said suspending the search was “not an easy decision” and offered condolences to the victims’ families and gratitude to the agencies that assisted in the operation.

The cause of the crash remains under investigation.