Answer the following question: Given the following passage "On Thursday, September 15, 2011, more than 500 people from Hongxiao Village protested over the large-scale death of fish in a nearby river. Angry protesters stormed the Zhejiang Jinko Solar Company factory compound, overturned eight company vehicles, and destroyed the offices before police came to disperse the crowd. Protests continued on the two following nights with reports of scuffles, officials said. Chen Hongming, a deputy head of Haining's environmental protection bureau, said the factory's waste disposal had failed pollution tests since April. The environmental watchdog had warned the factory, but it had not effectively controlled the pollution, Chen added.", answer the following question. Note that the answer is present within the text. Question: What entity tried to prevent the problem?
Answer:
police