Allegations by an investigator who looked into the crash of Swissair Flight 111 near Peggys Cove, N.S., and says that it might have been caused by an incendiary device are sparking surprise and anger.

Retired RCMP sergeant Tom Juby, an arson investigator assigned right away to the Swissair file, told CBC's The Fifth Estate that high levels of magnesium — a key ingredient in an incendiary device — were discovered in the cockpit area of the plane. Several other investigators and a federal scientist who The Fifth Estate spoke to supported Juby's informed suspicions.

The Transportation Safety Board (TSB) of Canada said that it was an accident caused by a fire in the cockpit, likely sparked by an electrical fault.

"We settled in with the notion believing fully that this was indeed an accident and there was no foul play or anything sinister going on and we've, over the last 13 years, have come to deal with that as the reality," David Wilkins, whose 19-year-old son was on the flight, told CBC's Connect with Mark Kelley.

"Just the outside shock that there was more going on here than just a simple accident kind of unleashes the whole memory of this thing and causes you at least to experience the notions of dismay, maybe disgust, outrage that this could even be a possibility."

In an interview with The Fifth Estate, Lynn Romano, who lost her husband in the crash, said she stands behind the investigation

"I'm convinced with everything that I've learned that a wiring issue took this plane down," she said.

"It surprises me in the sense that it’s never ever been suggested before," said Nova Scotia Premier Darrell Dexter. "Whether or not there is any basis for it or not it's not something you could imagine.

"I think everyone remembers those fateful hours following that event and the dissection that was done of the course of events over time and none of them ever seemed to suggest that. I think you have to leave it with the experts at the Transportation Safety Board to examine the evidence and decide what the actual cause was."

Watch The Fifth Estate documentary

The Fifth Estate investigates the crash of Swissair Flight 111 and reveals more on the stunning allegations on Friday, Sept. 16, at 9 p.m. on CBC-TV (9:30 p.m. NT). The documentary will be rebroadcast on CBC-TV on Sunday at 11 p.m. (11:30 p.m. NT) and on CBC News Network on Sunday at 7 p.m. ET and Tuesday at 10 p.m. ET/PT.

The flight from New York to Geneva crashed into the Atlantic Ocean on Sept. 2, 1998, killing 229 passengers and crew. The plane carried a Saudi prince, a relative of the former shah of Iran and high-profile UN officials. A half billion dollars of diamonds and gems were also never found.

Myron Ratnavale, who lost both parents and several friends on the flight, criticized Juby's theory.

"I just find it very, very far-fetched and I think it's an insult to the Canadian investigation team," he told The Canadian Press from his home in Geneva.

"I have full faith in them and I don't believe a word of it."

In response to an earlier request for an interview by The Fifth Estate,  Chantal Laflamme, a TSB spokeswoman said the report is the board's final word on the investigation.

"The board will not discuss possible criminality as this did not, in the opinion of both the TSB and the RCMP, play a role in the tragic accident," wrote Laflamme.

In an email to The Canadian Press, Julie Leroux of the TSB, said that no one from the board was available for an interview on Juby's allegations.

But she said if there had been evidence of a criminal act in the crash, the RCMP would have taken over as lead investigator because the board cannot conduct criminal investigations.

Leroux said the board used a Natural Resources Canada laboratory to determine if arced wires recovered from the crash started the fire or were the result of the fire.

"During this analysis, the expert, Dr. Jim Brown, found magnesium and other elements on some of the wires. Dr. Brown concluded that the presence of a minor amount of magnesium was a result of long exposure to seawater," she said.

Brown told The Fifth Estate that a year into the investigation, using auger electron spectroscopy, he discovered suspicious levels of magnesium — 10 times the anticipated amount — and other elements associated with arson in melted wiring from the section of the plane that suffered the greatest fire damage.

"There was a lot of magnesium. More than I would have expected," he said.

Juby said the RCMP did not support his findings and that he was pressured to stop his own inquiries. He said the RCMP brass ordered him to remove any reference to magnesium or a suspected incendiary device from his investigative notes.

Sgt. Julie Gagnon said in an email statement to The Canadian Press that Juby's complaint was reviewed by the RCMP's ethics adviser and the Mounties stand by the findings of that review, which it will not make public.

With files from The Canadian Press