The Minot Train Derailment occurred in Minot, North Dakota on 18 January 2002. At approximately 2:30 a.m. local time, a Canadian Pacific train derailed about 4 miles west of the city center, in a development called Terracita Vallejo. Tanker cars carrying anhydrous ammonia ruptured, spewing out a huge cloud of poisonous gas that quickly enveloped adjoining residential areas. The anhydrous ammonia spill was the largest such spill in U.S. history.

Emergency response to the disaster was confused at best. The late hour was a problem, as many media outlets were offline or unstaffed: KMOT was the only television station on air at the time; KXMC rushed to air early to cover the disaster; KXND and KMCY, without production staff, did not interrupt programming when they came to air.

Clear Channel Communications was blamed for not keeping overnight staff at its Minot stations; no emergency warning was issued for several hours while Minot officials located the station manager at home. The incident has been cited as an example of the physical dangers of media consolidation. Source

In excess of 300,000 pounds of anhydrous ammonia was released from the ruptured tanker cars. One tanker car was propelled over 600 feet in the air and skidded another 500 feet on the ground, crashing through a corner of a nearby house. Part of another tanker car landed on the ice of the Souris River.

.A dense anhydrous ammonia cloud drifted through low lying areas of the city. A temperature inversion, with sub-zero temperatures and no wind, prevented the cloud from dissipating. One fatality occurred, 15 people were hospitalized, and eventually over 1600 people sought medical treatment for anhydrous ammonia exposure. Source (PDF)

911 Calls in North Dakota Town Reveal Dangers of Media Consolidation from Democracy Now - Listen (MP3)