It was a long natural-gas pipeline; when the techs running it noticed a pressure drop, they didn't want to have to fill out forms or take any blame, so they just cranked the pressure back up and went back the normal routine. They didn't want to make a fuss. It was probably some minor thing, right?
Too bad is wasn't a defective pump or a problem at the source. It was a leak. It leaked out for three hours. The pipeline was in close proximity to a railroad and when two trains passed through the cloud, there was, unsurprsingly, a spark.
What resulted was possibly the most powerful non-nuclear explosion ever, estimated at 10 kilotons: the Ufa train disaster.
It happened in 1989, in what was then the Soviet Union.
Yes, another Chernobyl-esque triumph of communism! Not caused by earthquake, tidal wave or even gloom of night; brought about by guys who followed the written procedure, didn't question orders and weren't about to wake up the boss unless things were totally out of control -- and who, by so doing, let things get far past that point.
Remember that, next time someone hectors you about eeeeevil capitalism.
STANCOR 10P TRANSMITTER: UPDATE 12
9 hours ago