Saturday marks 80 years since a natural gas leak caused an explosion killing nearly 300 students and teachers at a school in Rusk County. It was the deadliest school tragedy in American history, yet one that is often forgotten.

On March 18, 1937, an employee at the London School in New London started an electric sanding machine in a part of the building he did not realize contained leaking gas. It launched a chain reaction that sent flames swirling beneath the building, causing the roof and walls to collapse – burying victims beneath.

As one website dedicated to the disaster explains, the magnitude of the explosion was so great that a two-ton slab of concrete was thrown 200 feet away, crushing a Chevrolet. An estimated 294 victims died.

At the time, the New London School District was among the wealthiest in the country, thanks to the profitable East Texas Oil Field. Though most Americans were struggling in the final years of the Great Depression, the Texas State Historical Association describes the school building as modern and steel-framed.

In the aftermath of the explosion, investigators discovered the school district had tapped into a residue gas line to save money, but a poor connection caused the odorless natural gas to accumulate under the school undetected, the historical association explained. Because of the tragedy, the Texas Legislature passed legislation requiring an odor be added to natural gas, so leaks could be easily detected in the future – preventing more deaths.