Five members of the bomb squad have been removed from duty, Moore said.
Moore said bomb squad technicians were "operating with the best intentions'' in a stressful situation, but says if mistakes were made in estimating the weight of explosive material placed in the truck, "I will hold the appropriate individuals accountable.''
The resulting explosion destroyed the containment vehicle, with the blast injuring 17 people, and caused "significant" property damage in the surrounding area, Moore said. He added that 13 businesses, 22 residential properties and 37 vehicles were damaged or destroyed. No deaths were reported.
South LA fireworks explosion: Some residents file claims against city after catastrophic detonation
According to Moore, bomb squad technicians estimated they were placing about 16 pounds of explosive material in the containment truck, which was capable of handling a blast of up to 24 pounds. But the actual amount of explosive weight placed in the vehicle appears to have exceeded 42 pounds.
"We have miscalculations that are significant,'' Moore said.
An investigation is ongoing. The ATF expects to conclude its investigation in 30 to 60 days.
Moore said the bomb squad has already begun implementing new procedures as a result of the explosion.
The explosion has heightened tensions among South Los Angeles residents, many of whom are demanding full accountability from the LAPD and accusing the department of showing disregard for the neighborhood by detonating fireworks in the middle of a lower-income residential area. Some have suggested that department members face criminal charges.
During Moore's news conference, one protester began shouting at the chief, hurling expletives and demanding his resignation or firing.
At 3 p.m., a 27th Street Incident Community Resource Center to assist affected residents will open at the YMCA at 1006 E. 28th St., according to the office of City Councilman Curren Price. The resource center will serve as the designated location where victims can connect with a wide range of services, including opportunities to file a claim, obtain mental health and wellness referrals, as well as other supportive services
Transitioning from the Local Assistance Center at Trinity Recreation Center, the new site will include representatives from Price's office, the city attorney and city clerk, mental health and wellness staff, as well as members of the non-profit All Peoples Community Center, who will offer food and clothing.
South LA explosion: Community demands accountability from LAPD following fireworks blast
Since the explosion, victims who were forced to evacuate their homes have been provided with access to housing, funds for basic needs like clothing, as well as three meals a day.
"The truth of the matter is, the victims of this explosion do not have the luxury of waiting. People are hurting, and they need help now,'' Price said. "At this moment, we are left to pick up the pieces, and we need to do whatever we can to help the people that are suffering.''
Authorities have said about 32,000 pounds of fireworks were being stored at a home on East 27th Street, from where they were being sold. The home's resident, Arturo Ceja III, 27, was charged with illegally transporting tons of explosives. He is set to be arraigned Aug. 2.
Prosecutors said Ceja purchased most of the explosives from a dealer in Pahrump, Nevada. In addition to the commercial fireworks, the initial search of Ceja's residence led to the discovery of more than 140 other homemade fireworks -- typically referred to M devices of varying sizes -- as well as explosives-making components, including hobby fuses that matched the fuse on a homemade mortar shell wrapped in tin foil discovered inside the residence, according to a court affidavit.
City News Service contributed to this report.