An explosion at a Kazakh copper mine belonging to Kazakhmys, the biggest copper producer in the country, killed three and injured one today. The blast occurred at about 10 a.m. local time, London- based Kazakhmys said in an e-mailed statement. “There are no people remaining at the mine,” Zulfira Mukhamediyar, a company spokeswoman, said by telephone from Almaty, Kazakhstan. “The cause of the blast is being looked into.”