(ANSA) - BELGRADE, MAY 12 - This morning an explosion occurred at a chemical factory in the town of Kocevje, in Slovenia, the Slovenian news agency STA reported. The explosion caused a fire and a tick smoke over the city. According to a preliminary estimate, more than 20 people were injured in the incident. Since the origin of the fire is not clear, residents were urged to stay indoors and close the windows. According to the Slovenian Civil Protection and Disaster Relief, the fire has now been put out, STA informed. (ANSA).