(Adds ThyssenKrupp comments, background)
RIO DE JANEIRO, July 28 (Reuters) - Regional prosecutors in Brazil's Rio de Janeiro state filed a lawsuit on Thursday to block the granting of an operating license to ThyssenKrupp AG's CSA plant until a thorough environmental assessment is conducted.
In a statement, Rio de Janeiro state's prosecutor-general office said the steel slab plant, which is located in the city of Santa Cruz, has agreed to adapt equipment and industrial processes to address concerns over potential environmental damages.
Prosecutors said they want to stop production at the plant, which has been operating since 2010 with pre-license authorization, not a definitive one. In a statement, they said the plant has been the target of pollution lawsuits.
A ThyssenKrupp spokesman said the state's suit does not affect the operation of the plant. The German company says it has fulfilled all requirements and expects to get the license.
ThyssenKrupp has been the sole owner of CSA since April, when Vale SA transferred its stake for a token sum, allowing the German company to possibly relaunch a sale process.
The plant in Rio de Janeiro state cost ThyssenKrupp and Vale $10 billion to build in the 2000s and was Brazil's most expensive ever foreign investment project. (Reporting by Rodrigo Viga Gaier; Writing by Guillermo Parra-Bernal and Tatiana Bautzer; Editing by Bill Trott)