virudhunagar, April 20 -- At least 23 people were charred to death, and six others sustained grievous injuries following a massive explosion at a private firecracker manufacturing unit near here, police said on Sunday. According to police and fire service officials, four of the six injured are in critical condition and are undergoing treatment at the Virudhunagar Government Medical College Hospital. The explosion occurred at the 'Vanaja' fireworks factory owned by one Muthumanickam, in Kattanarpatti near here. The place is located within the Vachakarapatti police station limits. Preliminary investigations suggest that the unit reportedly holds a license from the Petroleum and Explosives Safety Organisation (PESO), Nagpur. Over 100 labourers were reportedly engaged in work in the complex. The blast is believed to have originated in the front veranda area, where workers were allegedly handling raw materials and engaged in the final stages of manufacturing firecrackers.The impact of the blast was so severe that at least three rooms were reduced to rubble, and several adjacent structures were completely levelled....