In Uttar Pradesh, three persons were killed and many fell ill in a gas leakage incident at a chemical factory in Sandila industrial area of Hardoi district on Saturday.Quoting district police sources, AIR Allahabad correspondent reports, the incident occurred last night when gas leaked from a drug manufacturing Unit.The three persons including a woman who lost their lives in the mishap were workers of nearby factories.Five seriously ill persons have been shifted to Lucknow for treatment.The area police officer told AIR that leakage has now been blocked. Investigations are on to ascertain the cause of incident. .