US authorities are searching for six people after a medical plane bound for Boston, Massachusetts, went missing early Saturday morning.

The Federal Aviation Administration told the BBC that it lost contact with the Gulfstream G-100 plane and put out a search-and-rescue notice just after 1:00 local time (6:00 GMT).

An air and water search is underway off the coast of Nantucket, a Massachusetts island, according to the US Coast Guard's Northeast District.

The plane departed from Bermuda's L.F. Wade International Airport at 23:40 local time, according to flight data from FlightAware, and was slated to land at Boston's Logan International at 1:30 EDT (6:30 GMT).

According to the tail number released by the Coast Guard, the plane belonged to Latitude Air Ambulances, a company that provides international medical flights for patients returning home.

Among those on board were two pilots and two medical staff, both Canadian, Clarence Togeretz, director of flight operations at Latitude, told CBC News.

The crew flew to Bermuda to collect a patient and their relative, who are not Canadian, Togeretz said.

FlightAware's tracker shows the aircraft significantly dropped in altitude before its communications went dark, plummeting from around 7,300m (24,000ft) to 3,300m (11,000ft).