Bhubaneswar, March 6 : At least four people were killed and four others seriously injured in a major explosion at an illegal firecracker manufacturing unit in Odisha's Khurda district on Monday. The incident took place near Bhusandpur village under Tangi police limits. The explosion occurred when the victims were reportedly making firecrackers for the Dola Utsav, which is observed during Holi. However, the exact cause of the explosion is yet to be ascertained. After getting information at around 10.45 a.m., local police and fire service personnel rushed to the spot and rescued the four injured persons, and sent them to the district headquarters hospital (DHH), said Khurda collector K. Sudarshan Chakraborty. "The firecracker unit was operating illegally. No license was issued for it. We will investigate the incident and take strict action against the concerned persons," the collector said. He also informed that only one of the deceased has been identified while the process is on to get the identification of the others. Meanwhile, two of the injured with very severe burn injuries have been referred to AIIMS Bhubaneswar, an official of the Khurda hospital said. /IANS