On March 18, 1937, a catastrophic natural gas leak caused an explosion that destroyed the London School in New London, Texas, killing 425 students and teachers. The school, built in a wealthy oil-boom town, had recently tapped into an unprocessed gas line to save money, and the odorless, colorless gas accumulated in the building's crawlspace before being ignited by a spark from an electric sander. The blast was so powerful that it lifted the roof, threw a two-ton concrete block 200 feet, and was heard up to four miles away, while students had previously complained of headaches from the undetected leak. The disaster remains the third-deadliest in Texas history, surpassed only by the 1900 Galveston hurricane and the 1947 Texas City disaster. The explosion occurred just as younger students had been dismissed and while a PTA meeting was underway in a nearby gymnasium, sparing some but leaving hundreds of others trapped in the collapsed main wing. The event underscores the dangers of unregulated natural gas, as the school board had overridden the architect's plans to install cheaper gas heaters and had tapped into a residue line without authorization.