By Monica Houston-Waesch

FRANKFURT--German energy firm EnBW Energie Baden-Wuerttemberg AG (EBK.XE) on Thursday said the creditors of the insolvent wind energy company Prokon Regenerative Energien GmbH have rejected its offer, opting to restructure the company themselves.

In May, EnBW offered 550 million euros ($611 million) for Prokon.

In a statement, EnBW said it believed the the two companies would have fitted well together. "We wish the company Prokon, its employees and owners well and much success in the future," EnBW said.

EnBW said it would renew its growth efforts, noting it has earmarked EUR3.5 billion for renewable energy investment, and a further EUR3 billion to expand power grids over the coming years.

Prokon, which operates 50 wind parks in Germany and Poland, filed for bankruptcy in January 2014, exposing investors to potential losses of EUR1.4 billion and leading German politicians to toughen laws to protect investors.

--Neetha Mahadevan contruibuted to this article.

Write to Monica Houston-Waesch at nikki.houston@wsj.com

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