BBC's Rob Watson: "All evidence points to mechanical failure"

Swissair flight 111 from New York to Geneva plunged into the sea off Nova Scotia about 16 minutes after the pilot reported smoke in the cockpit.

He had been heading for Halifax to make an emergency landing and was just 10 minutes from the airport when the plane crashed.

Officials said none of the bodies so far recovered appeared to be burned, indicating that there was no explosion or large fire. Divers are still searching for more bodies and wreckage but they believe the chances of finding any survivors are remote.

The airliner, a McDonnell Douglas MD11, disappeared from radar screens at 02.30 BST on Thursday, about an hour after leaving New York's John F Kennedy International Airport.

It reportedly dumped several tons of fuel moments before crashing. Rescuers who were on the scene within 40 minutes reported a heavy odour of aviation fuel.

Keith Anderson, of the Canadian Air Traffic Association, said the pilot had not suggested the situation was desperate in his last communications with a control center in Moncton, New Brunswick.

"The initial call was to report smoke in the cockpit and the captain indicated an abnormal situation," Mr Anderson said.

"He used the term PAN which implies an emergency situation, but not a desperate situation."

When the black box is recovered experts will study recordings of conversations with air traffic controllers for clues to the crash - the worst in Swiss aviation history.

Dick Derden, chief investigator with Canada's Transportation Safety Board, confirmed that the pilot had begun to turn for an emergency landing in Boston when Canadian air traffic controllers told him to go to Halifax.

This meant the plane changed direction twice in the crucial minutes before it ditched in the sea.

Explosives experts called in

Canadian and US officials said there were no indications the crash resulted from sabotage, but investigators have still not ruled anything out.

Following the crash, the FBI searched JFK airport for any evidence linked to the tragedy.

The Royal Canadian Mounted Police have also called in explosives experts to examine debris for signs of a possible bomb blast.

If a criminal cause is eliminated, the investigation could be accelerated because the collection of material will not be slowed down by strict procedures regarding rules of evidence.

Swissair and aircraft manufacturer Boeing, who took over McDonnell Douglas last year, are sending independent investigation teams to the crash site.

Clean bill of health

Swissair President Jeffrey Katz said the plane was delivered in 1991.

Local people volunteered for crash search

It underwent a one-day complete check on August 10 following a general refit in 1996.

Mr Katz said so far there was "no indication about the potential cause of the accident of any sort. It had a clean bill of health and had complied with all maintenance requirements and quite recently."

Swissair, which has 16 MD11s in its 63-plane fleet, has one of the world's best safety records.