At least four people died in an oil depot fire in Ukraine's Kiev region, the UNN Ukrainian news agency reported on Tuesday citing a source in the country's State Emergency Service.The source said four people died in the fire, adding that all of them were firefighters.According to the State Emergency Service of Ukraine, firefighters extinguished the fire in one fuel tank, while 16 more are still burning."As of 7 a.m. on June 9, the fire in one 900-cubic-metre fuel tank has been put out, firefighters continue extinguishing 16 more tanks," the State Emergency Service said.The prosecutor’s office of the Kiev region has opened a criminal investigation into the incident under the article, "Violation of safety rules in explosive facilities or in explosive workshops."