July 1 (UPI) -- At least 17 people were injured and buildings were damaged in a "significant explosion" that occurred Wednesday while authorities were disposing of illegal fireworks in South Los Angeles.
The Los Angeles City Fire Department said in a statement the explosion happen in a bomb disposal trailer where bomb squad officers were in the process of seizing more than 5,000 pounds of illegal fireworks.
"Some of the fireworks were being stored in our Bomb Squad trailer as a precautionary measure," the LAPD said on Twitter. "Unknown at this time what caused an explosion."
At least 16 people were hospitalized, the LAFD said. Six were over the age of 50, three had moderate injuries and two were minor.
A total of nine officers received minor injuries, as did an an agent of the Bureau of Alcohol, Tobacco, Firearms and Explosives.
The LAFD said about 10 pounds of explosives had been placed by the bomb squad into its specialized detonation vehicle, which was destroyed in the blast.
LAPD Chief Michel Moore told reporters during a Wednesday night press conference the vehicle should have been able to withstand the explosion.
"Something happened in that containment vehicle that should not have happened, and we don't know why," Moore said. "But we intend to find out why."
Authorities said a 27-year-old man was arrested for illegally bringing the fireworks into California from out of state with intent to sell them ahead of the July Fourth weekend.
Los Angeles Mayor Eric Garcetti tweeted that he was "deeply concerned for those who were injured" and has directed police to conduct a full investigation.
"Illegal fireworks pose a great danger and can cost lives," he tweeted. "We will prosecute those who use or possess them to the fullest extent of the law."
Ahead of the holiday weekend, the city has been warning residents that all fireworks are illegal in the city of Los Angeles.
On June 23, City Attorney Mike Feuer announced a crackdown, saying he's sent cease and desist letters to Facebook, Craigslist and other sites that hosted offers for the sale of fireworks.