Six company executives have been detained after the firm's chemical factory exploded late on Monday night in Shandong province, killing one person just three weeks after catastrophic blasts in the port city of Tianjin . The factory in Lijin county exploded before midnight on Monday and the fire was brought under control about five hours later, according to the Dongying News website, run by the local city government. The six executives, from the Shandong Binyuan Chemical Company that runs the factory, had been detained, the website said. The cause of the explosion was under investigation. The company, located in the Lijin Binhai Economic and Technological Development Zone, produces adhesive materials. It did not answer calls for comment. Calls to the Lijin propaganda department were not answered. The blast area is 300km from Tianjin, where the huge explosions on August 12 at a warehouse area storing hazardous chemicals killed at least 159 people, many of them firefighters. The warehouse area was located closer to residential buildings than permitted under safety regulations for the storage of dangerous materials . State media yesterday for the first time reported remarks over the Tianjin blasts by a senior politician, who served as the Communist Party's city boss in the port city before rising to the top echelon of politics. Vice-Premier Zhang Gaoli , one of seven members of the top-level Politburo Standing Committee, had convened seven video conferences and issued 29 instructions for the rescue operation and investigation, the city's official news portal reported. In the aftermath of the blast, media reports have questioned how the warehouse's operator, Ruihai International Logistics, was able to secure official approval to convert a logistics centre near residential areas and highways into what was, effectively, a time bomb. The investigation should be transparent and offer honest explanations to the public, Tianjin Mayor Huang Xingguo quoted Zhang as saying. Before joining the Politburo Standing Committee in 2012, Zhang spent five years as party boss in Tianjin. Binhai New Area, where the blast took place, was the hub of the port city's economic growth during his tenure. Official media had previously not carried any comments from Zhang about the blasts, even though his immediate boss, Premier Li Keqiang , had inspected the disaster area. Zhang's portfolio focuses on economic and financial issues, while industrial safety falls to Vice-Premier Ma Kai . Ma's comments were also covered by official media. Hong Kong-based China watcher Johnny Lau Yui-siu said Zhang's remarks could be an effort to distance himself from the officials held responsible. "It means the leadership has decided how high up the investigation will go," Lau said. "Zhang Gaoli will not be held responsible for the blast."