Initial reports from the scene near Halifax's main airport suggest the Boeing 747's tail hit the runway during takeoff before crashing into a wooded area near an industrial park. Pictures from the scene show an orange glow in the sky not far from a rural road.
Some remains of the seven crew members have been recovered, said Constable Joe Taplin of the Royal Canadian Mounted Police.
The dead crew members were all males. Six were from Zimbabwe while the seventh was South African, said Steve Anderson, a spokesman for MK Airlines of Britain.
The weather at the time was good with clear skies.
The aircraft, which had stopped in Halifax to refuel, was loaded with tractors, lobsters and fish, and was bound for Zaragosa, Spain.
"There was a fire at the aircraft," Taplin said. "Emergency crews are done there right now and they're fighting a fire at the aircraft."
Witness Peter Lewis was dropping off his wife at the airport and saw two explosions that resembled heat lightning.
"As we were approaching we saw what I thought was heat lighting," he told radio station CJCH.
"That was only a quick one followed by a second one that was bigger. And then we seen a very bright orange light and I mean bright. It took up the whole sky."
The airport is located in a remote area outside Halifax's city limits.
The Transportation Safety Board of Canada is assembling a team of investigators in Ottawa, said spokesman John Cottreau.