At least 21 workers were hospitalized, one with severe burn injuries, after a chemical leak from a tank inside a plant at Nira-Nimbut in Purandar taluka on Wednesday, police said. Local villagers, however, claimed there was an explosion at the plant and pegged the number of affected workers at more than 40. They said three workers were critical. The affected workers have been admitted to different private hospitals in Nira and Lonand. "Around 4.30pm, the chemical overflowed from the tank. As per our information, 21 people were initially admitted to the hospital. One of them, with severe burn injuries, is in a serious condition," Pune rural superintendent of police Sandip Patil said. The plant authorities immediately shut the valve and contained the leak, police said. Nira village has a population of 20,000, some of whom work at the plant. After the incident, word quickly spread with differing reports of the severity. The affected workers complained of breathing difficulty, burning sensation in the eyes, nausea and dizziness, villagers said. "Around 4.30pm, a tank was overfilled with acetic anhydride, which caused a pressure build-up inside, leading to the explosion. Around 35-40 workers were rushed to the hospital," said Vaibhav Konde, a resident of the village. The chemical hung in the air for several hours after the incident, causing discomfort and breathing difficulty to the villagers. "Some of the workers who were exposed to the strong-smelling chemical lost consciousness. Others who fled from the place experienced dizziness, burning sensation in their eyes, breathing difficulty and nausea," said Sachin Vilas More, president of Nira River Sangharsha Samiti and a resident of Nira village. He said 42 workers were hospitalized, with the condition of three serious. More said he and other villagers have been protesting against the chemical plant ever since it had become operational in Nira-Nimbut - around 75km from Pune - in 2006. "We formed a protest committee in 2009 when we realized the plant's effluents were polluting the Nira river. We have also filed a PIL in the Bombay high court. The consequent probes by different committees appointed by the high court also found a high level of pollution in the water," More said. "The incident occurred at around 4.30pm, but we were informed around 6.30pm. By the time we reached the place, the plant officials had already rushed the workers to different hospitals," an official of the state's emergency ambulance service, 108, said. Acetic anhydride is used as an intermediate to produce a variety of acylated products. Its major use is in the manufacture of cellulose acetates. Other uses include the manufacture of analgesics and a variety of other products.