A large explosion Wednesday afternoon in the 500 block of Johnson Avenue in Pacifica that shattered windows in two houses seemed to be caused by a large "commercial grade" firework misfiring, police said Thursday.
San Mateo County's bomb squad and police who investigated the incident determined that the device probably was designed to launch from the ground and explode high in the air but malfunctioned and fell back to Earth before exploding in the residential neighborhood.
No one was injured.
Anyone with information is encouraged to call and speak with an officer at 650-738-7314.
Information may also be provided anonymously by calling the Silent Witness Tip Line at 650-359-4444.