Contaminated fuel isn't totally impossible but is highly unlikely since no other planes had an issue that day, and even with contaminated fuel the odds of the two engines shutting down so close together are quite low. The theory of the jet fuel being contaminated with avgas is also pretty much impossible at a big commercial airport like the one this jet took off from.
Something weird may have caused an electrical or electronic failure that took out both engines at once. Highly unlikely again but not impossible.
Another greater possibility is that one engine failed for some reason and the pilots reacted incorrectly causing the good engine to be shut down. This is the most likely and there have been other crashes caused by this kind of mistake. Pilots spend their whole careers maintaining equal thrust between a plane's engines, but then when an engine failure happens they have to go for maximum unequal thrust.