It all started shortly after 8 a.m. that day when longshoremen noticed smoke in the hold of the S.S. Grandcamp. The Grandcamp was a French cargo ship which had arrived to pick up a load of ammonium nitrate fertilizer. The ship already had fuel oil and ammunition in its cargo hold.
The Texas City Volunteer Fire Department was called but the fire continued to grow, and the hold of the ship continued to get hotter. According to the Texas City Library, the ship's captain tried to extinguish the fire by forcing steam into the cargo holds, but the steam vapors probably liquefied the ammonium nitrate to produce nitrous oxide, an extremely volatile substance.
The fire sent billowing smoke across the city. A crowd gathered at the docks to watch firefighters battle the huge blaze.
At 9:12 a.m., the ammonium nitrate detonated, sending a massive fireball hundreds of feet into the air. The explosion caused a 15-foot wave that crashed onto the docks and flooded surrounding areas. Windows shattered as far away as Houston, and vibrations from the blast registered on a seismograph in Denver, Colorado. A barge anchored in port was blown out of the water and landed 110 feet away.
Everyone standing nearby, including almost the entire Texas City Volunteer Fire Department, was killed instantly. Buildings near the blast were flattened and the neighboring Monsanto plant was destroyed.
Flaming debris triggered fires at nearby chemical plants and refineries.
The call for help was put out across the country and rescue workers from all over responded to the disaster.
The fire continued to burn into the next day, and at 1:10 a.m. on April 17, ammonium nitrate on a second ship exploded. That blast killed two more people and destroyed a nearby ship.
According to the Texas City Library, the high school gym was converted into a temporary morgue and a local auto mechanic's garage was used as an embalming room.
The exact number of dead was never determined. Estimates are that between 500 and 600 people died in the explosion. The exact number of dead was difficult to determine, because of the condition of many of the bodies and the fact that there were a number of visiting seaman and laborers, according to the Texas City Library. Thousands were wounded.
A memorial service was held for those killed in the blast and several months later, another service was held for those who were unidentified. According to the Texas City Library, the local newspaper, the Texas City Sun, ran an editorial describing all affected by the event as having been "bound together by a great and common tragedy for which there is no ready word of solace."