According to wikipedia, no one could agree on what was the specific cause of the fire. The landfill is the most commonly accepted, even with its variances. Honestly, I'm more apt to believe the locals. I would love to visit one day. Maybe after Zoe and I get a wagon again and can go on a road trip. Centralia was used as inspiration for the film adaptation of the video game Silent Hill. One of my favorite movies ever... especially within the genre. Life After People was a really awesome show. IIRC it started out as a single feature length documentary that was so popular that they made a series out of it. Its been a while since I watched it but I would like to again. Lots of cool info.
It took me a while to find it but here is the series 'Life After People' if any one would like to watch it. If anything should be free its documentaries. http://www.youtube.com/watch?v=6XDbcMND7fY&list=PL8115CA6F1D3A4807&feature=player_embedded EDIT: I'm watching the second episode now which starts out in Chicago. When I watched this for the first time years ago I had no idea that we were gonna move here and thus recognized none of the sites or locations... Not its all more familiar than the small town of 40,000 I lived in for 11 years.
Depending on what was dumped, spontaneous combustion is probable and not uncommon in areas where refuse collects during municipal strikes: http://www.gadling.com/2008/01/12/naples-city-of-garbage/
there is a 4x4 club that wheels in centrailia every year. they call it the annual "4 wheeling in hell"