Law enforcement briefed on an investigation into an explosion in Central Park over the July 4th holiday weekend say the blast was a result of a homemade explosive device.

Initial reports claimed the explosion was merely fireworks.

The New York Times reported, “Investigators believe it was part of an ‘experiment with fireworks,’ police officials said, and declined to call the material a device. The police said they do not believe it was connected to terrorism.”

NBC News also signed on to that narrative, saying “investigators suspect [the explosion] was caused by a homemade ‘experiment’ left behind by an amateur or hobbyist.”

New York Police Department Lt. Mark Torre said there’s no indication the blast was terrorism-related, wrote ABC News. “What seems likely at this point is that we have … an explosive hobbyist or an experimenter,” Torre said. “I believe we have somebody that made this material and then he wanted to test it.”

“The explosion could have been an experiment with fireworks or homemade explosives,” NYPD Deputy Chief John O’Connell said. “We believe this could have been put here as some sort of experiment.”

As it turns out, the explosion that maimed an 18-year-old tourist was not caused by fireworks after all.

According to CNN the explosion “was caused by the homemade explosive TATP.” TATP stands for triacetone triperoxide.

The chemicals used to make the improvised explosive were placed in a shopping bag, investigators said. The bag was pressure sensitive and activated when a tourist put his foot on it and triggered the explosion, suffering severe foot injuries. TATP is a notoriously unstable explosive that has been used in terrorist attacks for decades, including in the Paris attacks last fall and by the shoe bomber Richard Reid. It’s often made from common household chemicals, such as beauty supplies.

Investigators have traced the source of the device to a “defunct bakery in New Jersey.” They have not connected the explosive to any individual.

“These substances, which are commonly and legally available for sale in certain hardware stores, can be used in combination with other products to develop a home-made explosive agent,” according to a statement released by the NYPD Thursday. “Based on the crime scene investigation and the forensic examination, it is believed that this explosive material was made by someone experimenting with commercially available products.”

The police are offering up to a $10,000 reward for information that leads to the arrest of the responsible parties.