Four persons were killed and six injured in an explosion at a fireworks manufacturing shed at Padukkad near Thrissur on Thursday evening, police said.
The injured had been admitted to hospital.
Three persons were killed on the spot while another succumbed to injuries at the hospital.
The tile-roofed shed where fireworks were being prepared for the Paramekkavu Devaswom for the 'Thrissur Pooram' pyrotechnics festival was gutted in the blast.
Even though the shed was not in a thickly populated area, a few houses in the vicinity were damaged.
The workers were engaged in the final preparations for the sample fireworks display to be held tomorrow evening ahead of the `Pooram' on May 7.
The sample fireworks display has been cancelled following the accident.