``Our thoughts and our prayers go to the families of those killed in this tragedy,'' said Pat Chapman, a spokesman for the airport authority.
The tail of the Boeing 747 owned by MK Airlines Ltd. of Britain snapped off during takeoff and lay in a field at the end of the runway.
``The aircraft basically didn't take off,'' said Steve Anderson, an airline spokesman in Sussex, England.
``She continued her rotation and ran off the runway and ran into woods.''
There didn't appear to be casualities on the ground as there are no homes in the area.
The tail of the jet lay inside the fence surrounding the large airport property. The rest of the plane cut a wide, V-shaped swath through woods and brush and came to rest in pieces about a kilometre away.
``We've recovered some remains at the scene,'' said RCMP Const. Joe Taplin.
He said the RCMP were treating the crash as a potential criminal investigation after reports of an explosion. He didn't elaborate.
The tops of several trees and power poles were sheered off. The jet's severed wings lay in the brush, which was still burning in places several hours later.
A mangled engine and a charred portion of fuselage lay nearby.
``It's very devastating,'' firefighter Mike Larue said as he stood about 300 metres from the smouldering fuselage.
``It's surreal, is what it is. It's reality, but it's surreal for sure.''
The Boeing 747-200 crashed shortly before 4 a.m. local time near an industrial park and quarry about 30 kilometres north of Halifax.
Pictures from the scene showed an orange glow in the sky. It took about 60 firefighters and 20 trucks about three hours to control a fire caused by burning jet fuel on the ground.
Meanwhile, the crash forced the airport to close for several hours, delaying or cancelling 17 flights. Power was temporarily knocked out, but flights resumed on one runway later in the morning.
The plane's crew are either from the United Kingdom, South Africa or Zimbabwe, Anderson said.
Aside from the usual three-person crew in the cockpit, the plane was also carrying a loadmaster and a spare crew.
The weather at the time of the crash was good with a partly cloudy sky and light winds.
The huge aircraft, which stopped in Halifax to refuel, was loaded with lawn tractors and 53,000 kilograms of lobster and fish bound for Zaragosa, Spain.
Witness Peter Lewis was dropping off his wife at the airport and saw two explosions.
``As we were approaching we saw what I thought was heat lightning,'' he told radio station CJCH. ``That was only a quick one followed by a second one that was bigger. And then we saw a very bright orange light - and I mean bright. It took up the whole sky.''
The MK Airlines spokesman said the company had never had problems with this particular aircraft.
``She's been an absolute gem,'' Anderson said, noting the aircraft had been in service for about six years. He also said the company has been flying out of Halifax for the past 18 months.
The crash was the fourth for the cargo company in 12 years and the second involving fatalities. All three previous crashes were in Nigeria.
In 2001, one crew member was killed when a 747 went down about 700 metres short of the runway.
In 1996, a McDonnell Douglas DC-8F-55 struck trees during approach. There were no fatalities.
In 1992, a McDonnell Douglas DC-8 crashed and caught fire, also during final approach.
The information on the previous crashes is listed on a website for the Aviation Safety Network, an independent aviation safety watchdog.
The Transportation Safety Board of Canada has assembled a team of investigators in Ottawa. The board is an independent agency that investigates transportation accidents and prepares incident reports.
A TSB spokesman said the jet's flight date recorders had yet to be recovered.
The flight originated near Hartford, Conn., and the flight to Halifax was uneventful, Anderson said.
A pilot familiar with large planes said the tails of jets such as the 747 occasionally strike the ground during rotation - the point in the takeoff sequence when the pilot pulls back on the control stick, lifting the nose off the ground.
Large aircraft have so-called strike bars that protect the tail section when the pilot over-rotates and tail strikes the runway.
``It doesn't happen that often,'' said a pilot who didn't want his name used. ``You can encounter turbulence right at rotation.''
While tail strikes are uncommon, pilots can recover from them, he said.
In Ottawa, federal Transport Minister Jean Lapierre said ``my thoughts are with the families of the people involved in this tragic accident.''
Bill Fowler, a TSB spokesman, said the downed jet was likely equipped with depleted uranium, a radioactive material often used as ballast in the rudders and wings of wide-body aircraft.
Depleted uranium is the dense, heavy waste produced during the making of nuclear fuel and weapons.
A 747 may contain as much as 1,500 kilograms of the material, which is denser than lead and 60 per cent as radioactive as natural uranium.
Fowler said ``there is no threat or concern'' about exposure to those working on the wreckage.
