Five persons were killed and four others were critically injured in an explosion in an illegal cracker factory in Bijnor district of Uttar Pradesh.The incident took place on Thursday afternoon in Bakshiwala area in the house of one Yusuf, who was running a cracker unit in his house.The explosion was so severe that a part of the house was completely destroyed and the bodies of five labourers were buried under the debris.Sources said that the explosive material kept in the house caught fire which led to the explosion.The four seriously injured persons have been admitted to the district hospital.Senior police and civil officials have reached the spot and relief and rescue operations have begun.According to reports, Yusuf would lock the house form outside while crackers were being manufactured inside.The police have arrested Yusuf. Further details are awaited.