(Recasts throughout with Usiminas statement on injuries.)
SAO PAULO, Aug 10 (Reuters) - An explosion tore through Brazilian steelmaker Usinas Siderurgicas de Minas Gerais SA's largest plant on Friday, injuring 30 people and shaking the nearby town of Ipatinga, according to the company and firefighters.
The company, also known as Usiminas, said none of the injuries were severe and that most people had suffered "light bruising," adding that there were no fatalities.
The blast was centered on a huge barrel-shaped piece of equipment that stores gases released during the steel production process, according to the company. The plant employs about 6,500 people directly.
The blast was loud enough to be heard throughout the city of about 250,000 and sent a plume of smoke into the sky, according to Usiminas' press office and a firefighters' spokesman. The company said it halted the plant's blast furnaces temporarily.
The Ipatinga plant produced 813,000 tons of crude steel between April and June of this year, the company said in its latest earnings report.
Shares in Usiminas, one of the largest steel producers in Brazil, fell as much as 9 percent after initial reports of the explosion but later trimmed losses to about 6 percent.
"Our preliminary reading is that the impact on the stock is exaggerated," the Itau BBA analysts wrote, noting that the plant could be covered by insurance.
Ipatinga is a city in the state of Minas Gerais in southeastern Brazil, part of the so-called steel valley where other companies, including Arcelor Mittal, also operate plants. (Reporting by Alberto Alerigi Jr, Marcelo Teixeira and Marcelo Rochabrun; Additional reporting by Paula Laier; editing by Christian Plumb)