April 16, 1947, started out like any other spring day along the Gulf Coast in the town of Texas City, TX, population 16,000. Longshoremen busily loaded ships at the Port of Texas City and other townspeople went about their daily activities. The cargo ship Grandcamp was at the port taking on a load of ammonium nitrate fertilizer to be shipped to Europe as part of the rebuilding process following World War II.
Initially, the Grandcamp was scheduled to load the ammonium nitrate cargo at the Port of Houston. However, ammonium nitrate is not permitted to be handled at Houston, so transported to Texas City by rail from Nebraska and Iowa, the 32.5% ammonium nitrate fertilizer was placed into the hold of the ship along with a cargo of small-arms ammunition. Approximately 17 million pounds of ammonium nitrate was loaded onto the ship. Also in the harbor that day was the High Flyer, berthed approximately 600 feet from the Grandcamp on the same dock and loaded with 2 million pounds of ammonium nitrate and 4 million pounds of sulfur. By comparison, the bomb used in the bombing of the Murrah Federal Building in Oklahoma City in 1995 contained 5,000 pounds of ammonium nitrate and the bomb used at the World Trade Center in New York City in 1993 contained 1,500 pounds of ammonium nitrate.
Ammonium nitrate at a concentration of 32.5% is classified by the U.S. Department of Transportation (DOT) as an oxidizer and intended primarily as a fertilizer for agricultural and home use. Ammonium nitrate is also used as an oxidizer in the manufacturing of explosives. The ammonium nitrate that was loaded on the two ships at the Port of Texas City was coated with paraffin (a hydrocarbon product) and other chemicals to prevent caking of the material. Adding paraffin to the ammonium nitrate oxidizer is like combining fuel and oxygen, fulfilling two requirements of the fire triangle. All that is missing is heat. Because ammonium nitrate is also an oxidizer, under certain conditions it can become explosive. For an explosion to occur involving ammonium nitrate, confinement is necessary for the fuel and oxidizer before the heat is applied. As longshoremen were loading the ammonium nitrate on the ship, they reported that the bags were warm. This could have been caused by an exothermic (heat-releasing) chemical reaction going on within the bags. A chemical process resulting in spontaneous combustion can occur with chemical oxidizers at elevated temperatures.
At around 8:10 A.M., a fire was reported deep in Cargo Hold No. 4 of the Grandcamp, toward the rear of the ship on the lower level. Two fire extinguishers and a gallon jug of drinking water were applied to the fire area by the ship's crew with little effect. The captain of the ship ordered the burning hold sealed and steam injected into it. This was a common method of shipboard firefighting at that time. This confinement and injection of steam is likely to have resulted in the elevation of the temperature of the ammonium nitrate and the explosion that occurred.
Texas City's volunteer fire department responded to the initial report of fire with its four fire engines led by Chief Henry J. Baumgartner. It is unknown whether the fire department had any knowledge of the dangers of fires involving ammonium nitrate or potential explosives. A fireboat from Galveston was requested at about the same time by the ship's captain. Twenty-seven of the Texas City department's 28 volunteers answered the call along with the Republic Oil Refining Company firefighting team. The firefighters set up their hose streams along the dock and applied water into the burning hold of the Grandcamp. Smoke poured from the hold, followed by flames at around 9 A.M. The unusual color of the smoke caught the attention of many people. Some described it as a peach color, some called it reddish orange.