Questions are being raised about the safety record of a Boeing 747 cargo jet that crashed in Halifax on Thursday, killing all seven crew members on board. There were no Canadians on the flight.

The crash happened just before 4 a.m. local time in Halifax. Airport workers say they watched in horror as the tail of the aircraft caused sparks as it dragged along the runway. The tail then either ripped or fell off.

The plane was airborn for just a few seconds before slamming into nearby trees.

"It was like it was almost dragging -- the behind was dragging," eyewitness Darren McLaughlin told ATV News, an affiliate of CTV. He said the plane just seemed to blow up, "from white sky to an orange sky."

MK Airlines, the company that owns the crashed aircraft, is a British-owned cargo firm based in Ghana.

Capt. John Power, the operations manager for MK, arrived in Halifax Thursday evening. He told reporters he had come to join the investigating team, but would not answer questions about the airline's record.

"I am not here to defend, I'm here to try and support this investigation," Power said, adding that he would provide more information on Friday.

According to reports, MK Airlines has been involved in four crashes since 1990 -- all during takeoffs or landings. All three previous crashes were in Nigeria. In an accident in 2001, one crew member was killed in a crash during landing.

This crash is by far the worst, in terms of loss of life. Power described the nationalities of the seven crew members as:

Four United Kingdom passport holders; two living in South Africa, and two living in Zimbabwe

One German passport holder, also living in South Africa

Two Zimbabwean passport holders, living in Zimbabwe

"The families and all of MK are grieving the loss of our friends and our fellow airmen," Power said.

The investigation

The RCMP is treating the crash as a potential criminal investigation, following witness reports of explosions during the crash.

Transportation Safety Board investigators from Canada, the United States, the United Kingdom and Ghana are examining every piece of wreckage.

Bill Fowler, an inspector with the Transportation Safety Board of Canada, said it's too early to tell what might have caused the crash. "We're so early into this," he said.

Responding to questions about the plane's flying record, Fowler said they have not yet linked previous crashes with this accident.

"It's just a matter of course that we will look at that aspect. And what you have to make sure is that there is a clear link. And if there is a clear link, we will put those aspects together.

"But we do not lead to those conclusions at this stage."

Earlier, ATV reporter Marc Patrone reported that Fowler had said there is nothing to indicate the plane was too heavy, nor that there was an explosion before the crash, as some are suggesting.

The most important clue might be the jet's crumpled tail, which is lying in a field just off the end of the runway. The bulk of the charred aircraft is lying in pieces, hundreds of metres away.

When it came down, the plane snapped poles like toothpicks, ripped through power lines, and cut a swath through the bush at the end of the runway about the length of a football field.

"The disturbing and overall image that most strikes you is the wreckage itself, and the hulk of this fuselage -- nothing but a blackened centre of an aircraft torn into pieces," said Michael Tutton, the only journalist given access to the site.

The plane had arrived from Connecticut, and had just refuelled in Halifax, before heading to Spain. It was loaded with about 53,000 kilograms of fish.

It took 60 firefighters nearly three hours to douse the flames.

The jet's flight data recorders have yet to be recovered.

In Ottawa, federal Transport Minister Jean Lapierre said "my thoughts are with the families of the people involved in this tragic accident."

With reports from CTV's John Vennavally-Rao and ATV's Marc Patrone