A gas explosion on Friday at a Usiminas steel plant in Brazil's Ipatinga left around 20 people injured, officials said.Firefighters remain on the scene to investigate the cause of the incident and to determine the exact number of people who were injured, many of whom were taken to a nearby hospital by Usiminas' in-house emergency team, Efe reported.According to several residents, the explosion, which was heard and felt at several locations throughout the city, took place at around 1 p.m.The Minas Gerais state police evacuated the steel plant as well as nearby schools, although there was no need to evacuate residential buildings neighboring the plant, a fire department official said."The incident is now under control. There was an explosion of the gasometer (a storage vessel), and that explosion burnt or dispersed all of the gas it contained. There was no fire, no fatal victims, and the people who were injured were taken to the hospital," he said.Usiminas confirmed that the gasometer of the Ipatinga plant had exploded, adding in a statement that it was investigating the cause of the blast.As a precautionary measure, the company, one of the most important steel firms in Brazil, has temporarily halted operations in the Ipatinga plant.