Beijing, Shawwal 29, 1436, Aug 14, 2015, SPA -- The death toll in the massive explosion at a chemical warehouse in north-eastern China rose to 56 including 21 firefighters on Friday evening as details about the cause remained unclear, dpa reported. More than 1,000 rescuers were proceeding slowly and exercising extreme caution as they are uncertain which hazardous substances triggered the explosion, authorities in the port city of Tianjin said. At least 721 were injured when explosions and a fireball hit the warehouse late Wednesday. Twenty-five were critically wounded and another 33 were in a serious condition, Xinhua reported. --SPA 15:38 LOCAL TIME 12:38 GMT www.spa.gov.sa/w