(ANSA) - Taranto, July 26 - A judge ordered the partial shutdown of Italy's largest steelworks, the ILVA plant in the southern port of Taranto on Thursday. The judge also authorized the house arrest of eight ILVA managers and ex-managers after magistrates found the plant's fumes and dust endangered the heath of thousands of workers and residents nearby. The arrests ordered by judge Patrizia Todisco included the owner, Emilio Riva, chairman of ILVA until May 2010; his son Nicola Riva, who took his father's place as chairman until a few weeks ago; the ex-director of the Taranto plant, Luigi Capogrosso; the current head of the plant's coke ovens, Ivan Di Maggio; and the supervisor for the agglomeration area, Angelo Cavallo. The partial shutdown closes ILVA's mineral park, coke ovens, agglomeration area, blast furnaces, steel mills and iron materials management. The steelworks owned by the Riva family is under legal pressure as the result of a drawn-out investigation lasting more than a decade. Expert epidemiological and chemical assessments this spring concluded that the ILVA plant was responsible for an environmental disaster causing 386 deaths over the last 13 years and a range of illnesses in neighborhoods near the plant. Workers and labor unions have denounced legal action for fear of losing a major employer and a regional economic engine. On receiving news of the shutdown Thursday, 2,000 workers streamed out of the plants and into the streets. The protest followed another on Wednesday, in which thousands of workers blocked a highway. The steelworks is one of southern Italy's few large industrial plants, producing 30% of Italy's steel, and employing more than 11,000 workers. Italy's environmental minster Corrado Clini met with Puglia Governor Nichi Vendola and other officials in Rome on Thursday seeking an agreement on how to clean up the environmental damage and also salvage industrial production at the plant. Vendola said that if the case reaches trial, the Puglia region will join as a civil party.