UPDATE 1-French engineering group Spie joins the hunt for Engie's Equans

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PARIS, Sept 6 (Reuters) - French engineering group Spie confirmed on Monday it has submitted a non-binding offer to buy Equans, the newly-created services unit of French energy group Engie, joining an already crowded field of candidates.

French construction groups Bouygues and Eiffage have also said they are interested and sources told Reuters investment funds such as CVC-PAI Partners, Bain Capital and Carlyle could come up with an offer.

Non-binding offers for Equans, which could be worth 5-6 billion euros ($5.94-$7.12 billion), must be submitted before 5 p.m. Paris time on Monday.

In a statement, Spie said its offer would be financed by debt and existing financial resources and that bpifrance and Clayton Dubilier & Rice would help in financing the offer.

Engie CEO Catherine MacGregor said in June all options for the sale of Equans were being considered.

Engie is trying to simplify its structure by selling off some activities to concentrate on others such as renewable energy.

$1 = 0.8422 euros $1 = 0.8424 euros Reporting by Benoit Van Overstraeten and Sudip Kar-Gupta; Editing by Louise Heavens