* Final bids to be submitted by end-September -sources
* First State, Enovos among interested parties-sources
* Bids expected to reach 350-400 mln euros -sources
By Arno Schuetze and Christoph Steitz
FRANKFURT, Aug 5 At least four final bidders have been chosen for German regional gas grid operator EVG Thueringen, three people familiar with the matter told Reuters on Tuesday.
Jointly owned by German utility E.ON and gas firm VNG AG, final bids for EVG Thueringen are due to be submitted at end-September and are expected in the range of 350 to 400 million euros ($469-536 million), the sources said.
Bidders include First State Investments, regional utility Thueringer Energie and a consortium consisting of Luxembourg-based energy group Enovos and private equity firm Ardian, the sources said.
One of the sources added Frankfurt-based gas company Gas Union was also still interested in EVG Thueringen, which operates a 1,200-kilometre gas grid in the German states of Thuringia and Saxony.
E.ON, Thueringer Energie, Enovos and Ardian declined to comment.
First State Investments, Gas Union and VNG - which is part-owned by EWE AG, Russia's Gazprom and BASF's oil and gas arm Wintershall - were not immediately available for comment.
Sources told Reuters in February that E.ON and VNG are looking to divest EVG Thueringen.
Pension funds and infrastructure investors have been scrambling to get their hands on power and gas grids, usually regulated assets with fixed return, trying to escape volatile equity markets and ultra-low interest rates.
First State Investments, an asset manager owned by the Commonwealth Bank of Australia, has already bought E.ON's regional gas grid Ferngas Nordbayern GmbH and led a consortium which acquired the local power distribution grid of Finnish utility Fortum for 2.55 billion euros.
Enovos is partly owned by E.ON and RWE, which together hold 28.36 percent in the company, a stake they are aiming to divest.
One source familiar with the process said the companies are in talks to sell their share in Enovos to the Grand Duchy of Luxembourg, which already owns a 25.44 percent stake.
($1 = 0.7468 Euros) (Editing by David Evans)