Rescue workers near the scene

BLANDFORD, Nova Scotia (CNN) -- A Swissair jetliner with 228 people on board that was bound from New York to Geneva crashed off the coast of Nova Scotia on Wednesday evening.

A fisherman helping in the search described "a huge debris field" about three miles offshore and he said bodies have been found.

Halifax Emergency Health Services spokesman Grant Lingley said there may be survivors, but he is not sure. Lingley said people were found and they were on the way to a hospital, but he did not know how many or if they were alive.

"We don't have numbers at this stage, simply that they are arriving within the half-hour," Lingley said.

Rescue officials said four bodies were recovered as of 2 a.m. EDT Thursday.

A spokesman for the Canadian Transportation Safety Board said air traffic controllers reported that the pilot radioed that smoke was in the cockpit. Another official said information indicated the plane was attempting an emergency landing in Halifax because of the smoke.

Debris was found in the waters of the Atlantic near where the plane was last seen on radar, according to a Canadian Search and Rescue spokesman.

A New York Port Authority spokesman told CNN that Canadian officials confirmed to his agency that the plane was in the water and that a Swissair official reported the discovery of an oil slick.

Witnesses reported hearing an explosion and seeing a bright flash about the time the jet disappeared.

There were 228 people on board, including 213 passengers and 15 crew members, according to a Swissair spokeswoman Marian Van Zweren. Earlier, another Swissair spokeswoman placed the number at 229 people.

Canadian search and rescue aircraft were looking for the plane in an area south of Halifax, according to Canadian Coast Guard Lt. Cmdr. Mike Considine

Some pieces of debris were spotted more than two hours after the plane was reported missing, the Search and Rescue spokesman said.

Swissair flight 111 took off from JFK International Airport at 8:30 p.m. EDT and was scheduled to land at 3:30 a.m EDT (9:30 a.m.local) Thursday in Geneva, according to a spokeswoman for Swissair.

"It went down less than an hour later," said FAA spokeswoman Drucie Anderson.

A spokesman with the Canadian Transportation Safety Board, which will lead the investigation, said he had heard initial information that the Swissair pilot had reported smoke in the cockpit and was attempting and emergency landing at Halifax.

The MD-11 disappeared from radar Wednesday evening at 9:18 p.m. EDT about seven miles off the coast, south of Halifax, according to Considine

Canadian officials were mounting a search and rescue operation in the Atlantic Ocean, Considine said.

"We heard the sound of an engine going overhead and then shortly after we felt a large vibration on the house, almost as if someone was banging into the side of our house," said Linda Farmer, who lives near the coast in Blandford, Nova Scotia.

"There was quite a terrible explosion, but there was no flame that we could see," said Audrey Bachman, whose husband is a fisherman and is using his boat to help search for survivors.

Dozens of ambulances were assembled in the coastal area near where the plane is believed to have gone down.

Any survivors of the SwissAir crash would most likely be taken to the Queen Elizabeth II Health Sciences Center in Halifax, according to a hospital spokeswoman. The hospital is on alert to accept survivors and rescue teams have also been sent to the scene.

The QEII is the largest health care center in Atlantic Canada and the QEII Emergency Department sees about 70,000 people each year. The center is a teaching and research hospital with 11 buildings on four sites in the heart of Halifax.

A team of 10 investigators from the National Transportation Safety Board was to depart Washington's National Airport at 5 a.m., according to NTSB spokesman Matt Furman. Canadian aviation officials will be in charge of the crash probe, however.

The flight was a "code share" flight with Delta Airlines, which may have had some flight attendents on board, according to Delta spokesman Bill Berry.

The Swissair spokeswoman told CNN the MD-11 was built in August 1991.

Swissair provided a phone number for the family members of crash victims: 1-800-801-0088.