At least three bidders are in the running for the sale of Hochtief AG's (HOT.XE) airport portfolio, and the deal could conclude as early as September, several people close to the matter told Dow Jones Newswires Friday, adding .

Airport operator Fraport AG (FRA.XE) and its bidding partner, Deutsche Bank AG's (DB) infrastructure fund RREEF, as well as French construction company Vinci S.A. (DG.FR), submitted binding offers in time for the deadline Thursday, several people close to the matter said.

A bidding consortium made up of Allianz SE's (ALV.XE) investment arm Allianz Capital Partners and the infrastructure fund Global Infrastructure Partners, also submitted a bid, one of the people said.

A purchase price of up to about EUR1.1 billion is "realistic," another person said.

A question mark remains over whether Singapore's Changi Airport Group or HNA Group, the parent of Hainan Airlines Co.(600211.SH), China's fourth-largest airline by revenue, also bid for the unit. Recent media reports indicated the companies were interested in bidding.

-By Eyk Henning, Dow Jones Newswires: +49 69 29725 511: eyk.henning@dowjones.com

(Kirsten Bienk, Natali Schwab and Jan Hromadko contributed to this story.)