The explosion occurred at about 8:35 a.m. on Thursday, November 21, 1996 in the middle of a bustling commercial sector of Río Piedras.

[3] The immediate theory was that the explosion was caused by a bomb planted by clandestine paramilitaries or even arson because of previous deliberate acts.

United States President Bill Clinton declared Puerto Rico a disaster area, which ensured the receipt of federal aid to help the victims, including the assistance of the National Transportation Safety Board (NTSB), which launched an investigation.

After the explosion, bodies of victims were placed on the pavement in front of the nearby La Milagrosa church, where Cardinal Luis Aponte Martínez administered last rites.

[7] "There were just parts of bodies lying in the street, torsos, bones, cars blasted against the building," Police Chief Pedro Toledo said.

[8] The NTSB's investigation revealed that several persons had reported a gas leak in the building in the days leading up to the explosion, complaining about a bad smell in the store's basement.

The investigation showed that stored shoes were tossed up by the explosion, meaning that the fuel had to be at ground level.