The United States Coast Guard suspended a search for six missing people who were aboard an Ontario air ambulance that crashed off the eastern U.S. coast over the weekend.

In a press release shared Sunday night, Rear Adm. Matthew Lake, Commander of the Northeast District said, “suspending a search is not an easy decision.”

“We express our deepest condolences to the families and loved ones affected by the tragedy and our gratitude for our partner agencies who helped support search efforts,” he added.

Earlier in the day, officials said they were concentrating their search around a debris field that was located 20 miles off Nantucket.

Coast Guard crews along with the New York National Guard’s Air Rescue Wing and Massachusetts authorities searched an area encompassing 2,840 square miles (7,356 square kilometers) using fixed-wing aircraft, helicopters, boats and cutters.

“This is a large and demanding search area,” Lake said.

The depth of the water around the debris field was 80 to 90 feet (about 24 to 27 meters). The Coast Guard was in the process of deploying sonar to search the seabed floor, he said.

The plane, which is owned by Hamilton, Ont.-based medical evacuation company Latitude Air Ambulance, was transporting a patient and their family member from Bermuda to Boston when it disappeared around 1:30 a.m.

Six people, including four Canadians and two Bermudian nationals, were aboard the aircraft.

Air traffic audio indicates that the plane may have been “coming in blind” when a storm loomed ahead shortly before it vanished.

The pilot reported electrical problems and declared an emergency as the jet approached the coast, according to air traffic control audio posted by LiveATC.net. “Roger, you said you’re coming in blind. Is that what you said?” a controller can be heard asking the pilot.

That makes Mary Schiavo, who is a former Inspector General of the Transportation Department, think the plane may have lost its navigational instruments just as a storm moved across its path on radar. The plane also descended sharply from its cruising altitude of around 24,000 feet to around 10,000 feet, according to preliminary data from flight tracking site FlightRadar24.

“Something bad happened with this big drop, and they flew into this big storm. It’s a terrible place to have a loss of your instruments and be flying blind,” said Schiavo, who is an aviation attorney. “It’s very easy to get disoriented and not know if you’re turning, climbing, descending, etc.”

Files from The Associated Press were used in this report