Visakhapatnam (Andhra Pradesh): Seven people were killed and five others injured when an explosion took place at a firecracker manufacturing unit in Visakhapatnam. Six people died on the spot while another died while shifting a hospital. The reason behind blast is yet to be ascertained. The entire building went up in flames and people were trapped under the debris. District revenue officer K Nageswara Rao said that investigation was underway and further details were awaited. He also ruled out that the factory was illegal. "He is having a license, a valid license, now we have verified at the office records,” said Nageswara. Andhra Pradesh chief minister Chandrababu Naidu announced a compensation of Rs 200,000 for the families of the victims.