More than a dozen people were injured during a massive explosion that occurred in South Los Angeles on Wednesday when police attempted to safely dispose of seized illegal fireworks.

The explosion occurred around 7:40 p.m. on June 30 in the area of 27th Street and San Pedro in Los Angeles, California.

The Los Angeles Police Department (LAPD) responded to a home after receiving a tip and seized at least 5,000 pounds of illegal commercial-grade fireworks earlier in the day on Wednesday.

The seized fireworks were transferred to a “total containment” truck with an iron chamber designed to safely house explosives during a pre-planned detonation. The decision to detonate the fireworks in a residential neighborhood was reportedly made due to the risk of transporting the explosives to an off-site location.

However, LAPD Chief Michel Moore said that there was a “total catastrophic failure of that containment vehicle” resulting in a large blast.

“Some of the fireworks were being stored in our Bomb Squad trailer as a precautionary measure. Unknown at this time what caused an explosion,” LAPD said in a social media statement.

“Clearly protocols were followed and pursued, but something happened in that containment vehicle that should have not happened and we don’t know why. We intend to find out why,” Moore said.

Seventeen people were hurt in the explosion, including several police officers.

Several homes were also damaged and will need to be evaluated for structural damage.

Arturo Cejas III was arrested on suspicion of possessing a destructive device, according to ABC7.

A team from the ATF is investigation the explosion as of Thursday morning.