Ontario explosion: Cleanup underway after 2 killed when fireworks detonate prompting evacuations By Kelli Johnson and Mary Stringini Published Cleanup, investigation underway at Ontario fireworks blast site Authorities Friday will be destroying a massive cache of fireworks in an Ontario neighborhood that was rocked Tuesday by explosions that left two people dead. ONTARIO, Calif. - Authorities Friday will be destroying a massive cache of fireworks in an Ontario neighborhood that was rocked Tuesday by explosions that left two people dead. Tuesday's blast rained debris down over a wide area in the city of Ontario and prompted the evacuation of dozens of residents.