Benson, AZ – February 17, 2025
A routine freight train journey turned into a devastating disaster when Southern Pacific Transportation Company’s freight train 2nd BSM 22, carrying military munitions, exploded near Benson, Arizona, creating a massive crater and leading to rail safety reforms.
Around 1:40pm on May 24, 1973, Southern Pacific freight train 2nd BSM 22 departed El Paso, Texas on its journey from San Antonio, Texas to San Francisco, California. Around 4:30pm, the train departed Lordsburg, New Mexico. The train stopped in San Simon around 5:15 to investigate a report of smoke coming from braking. Nothing was found and the train continued, receiving two additional crew inspections and passed a hotbox detector as is traveled through Willcox.
Among its 106 cars, cars 35 through 46 carried 2,600 MK 82, 500-lb bombs.
First Explosion: Unknown to the crew, an explosion in one of the munitions boxcars blew out part of the car around 6:45pm, scattering bomb fragments and debris along the tracks. It occurred just west of the Dragoon Crossing. Although parts of the bomb and pallet were blown onto the track, it did not interfere with the trains operations.
A driver in a vehicle was on an access road adjacent to the track and extinguished smoldering embers after seeing the train travel through "mustard yellow smoke," which was likely vaporized TNT. According to crew statements, the rear brakeman who was in the caboose noticed a smoldering crosstie and grassfire near the track and notified the engine crew. The engineer saw smoke and began braking. The train began to slow down from 45 miles per hour to 30.
Second Explosion: Another detonation erupted from car 38 about four and a half miles later, launching six bombs, a side ladder, boxcar fragments, and other debris.
After applying the emergency brakes, the conductor and rear brakeman jumped from the caboose after seeing fire and smoke. A flash and ball of fire erupted from the burning cars. As car 98 passed through, one of the bombs that fell from car 38 exploded leaving a crater 115 feet by 93 feet and 25 feet deep.
The Blasts
Cars became separated and other freight hauling cars were damaged, spilling cargo like water heaters, zinc ash, asbestos, and car tires. The ground was scorched for a quarter-mile around the blast area. Explosions continued until around 1:15 the next morning. Three of the blasts registered on seismic scale at 1.2, 1.4, and 1.6. Eleven cars were completely destroyed and debris was blown around three-quarters of a mile away. Only 500 of the 2,600 munitions were recovered unexploded. Windows in a home five miles away were shattered and bombs were blown about a mile away from the scene. The only injuries were to the two crew members who jumped from the caboose.
First responders from Benson Police, Cochise County Sheriff's Office, and Arizona Department of Public Safety State Troopers responded to scene with a Fort Huachuca Demolition Team and Rural Metro Fire Department from Tucson. Both the Federal Bureau of Investigating and Naval Investigative Service investigated the accident to rule out deliberate acts.
Authorities ruled out sabotage or arson, instead attributing the catastrophe to operational failures, sparks from brake shoes burning flooring that was contaminated with sodium-nitrate from previous shipments, and outdated safety measures.
The Federal Railroad Administration adopted new changes at the time that required brake shoe spark shields when transporting a Class A explosive. Many other regulations have been implemented since this accident. Some of them involve spacing out cars with munitions, requiring additional oversight on selecting cars for munitions shipment, and cleaning and loading requirements.
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