At least 21 people have been killed and 61 injured by an explosion at a fireworks factory in central China. More than 500 rescuers have been dispatched to the scene after the huge explosion, which occurred at a facility in the city of Changsha in Hunan province on Monday afternoon, according to the state-run newspaper China Daily. The explosion occurred at 4.40pm on Monday, and the force of the blast shattered windows and damaged houses over a wide area near the factory, according to local media reports. Those living nearby were evacuated due to an ongoing risk of further explosions from two black powder warehouses at the site, a Xinhua report said. Aerial footage broadcast on Tuesday by Chinese state TV showed white plumes of smoke still billowing from parts of the site, operated by the Huasheng Fireworks Manufacturing and Display Co. The cause of the blast has not yet been confirmed but officials have taken “control measures” against those in charge of the company, without specifying what that means.…