Brazil's Andrade Gutierrez walks out of Cemig shareholder accord

BRASILIA, Sept 7 (Reuters) - In a surprise move, a unit of Andrade Gutierrez SA, a Brazilian infrastructure and energy conglomerate, decided to leave the controlling bloc of Cia Energetica de Minas Gerais SA, putting an end to months of tension with the Brazilian power utility's largest shareholder.

In a Thursday filing, the utility known as Cemig said that AGC Energia S/A, a subsidiary of Andrade Gutierrez, said it would sell its stake in the company through a bloc trade, without elaborating.

For almost 15 years, Andrade Gutierrez was part of Cemig's controlling bloc with the Brazilian state of Minas Gerais.

Efforts to contact Andrade Gutierrez outside business hours were unsuccessful. (Reporting by Guillermo Parra-Bernal; Writing by Silvio Cascione; Editing by Sandra Maler)