Spontaneous human combustion is sparking people’s attention once again.

The phenomenon of people spontaneously bursting into flames is one highly debated and unproven theory. For decades, investigators have been seeking evidence of its existence. Now, the Discovery Channel is airing a series of episodes that spotlights the theory of SHC. The first episode of "Investigation X" aired 10 p.m. Monday. Click here to see air times. The show features the work of mechanical and electrical engineer Larry E. Arnold, who studies the supernatural.

Arnold has documented about 300 cases from the last 200 years of people experiencing what seems to be SHC. He became fascinated in this mystery in 1951. That year, 67-year-old Mary Hardy Reeser, of St. Petersburg, Fla., was found dead – speculation swirled that she was a suspected victim of spontaneous human combustion.

Reeser, later nicknamed by the media the "Cinder Lady," was found mostly in ashes in her apartment. Her remains were on a chair in which she was sitting. Just a left leg remained. Objects around the house were unscathed – offering little evidence of a fire. SHC is believed to cause people to catch fire without apparent cause, burning them to ashes but leaving surrounding objects unaffected. And according to the FBI, tests showed no signs of "oxidizing chemicals, petroleum hydrocarbons or other substances that could ignite or accelerate combustion."

It led some to believe the SHC explained her death. Another explanation became known as the "wick effect," where the human body catches a flame and will literally burn itself out much like a candle wick. Others think that Reeser fell unconscious while smoking a cigarette and set fire to her pajamas.

In 1976 Arnold founded ParaScience International, which investigates the supernatural and gruesome unexplained incidents. Larry writes on his website that he hopes the Discovery Channel series will open up people to believe in the possibility of self combustion.

"We have high hopes that this program will at last be honest and unbiased about SHC," he writes on his website.

The same gruesome incident was caught in the 1984 film "This Is Spinal Tap." In the movie, one of the band’s drummers apparently spontaneously combusted on stage — leaving behind only a globule.

Watch this YouTube clip below to see a clip from the movie where the drummer bursts into a cloud of dust and fog.