* Board members probed for "aiding of market manipulation"
* Prosecutors charged ex-Porsche CEO, CFO last December
* Stuttgart prosecutors' investigation running since 2009 (Adds comment from prosecutors, background)
STUTTGART, Germany, Feb 12 German prosecutors have extended a probe into market manipulation to all members of Porsche SE's supervisory board, including carmaker Volkswagen's chairman, Ferdinand Piech.
Prosecutors are investigating the 12-member supervisory board of the German holding company, which owns about 51 percent of Volkswagen's (VW) shares, for suspected "aiding of market manipulation," a spokesman said, declining to be more specific.
The move follows a decision by prosecutors last December to charge the former chief executive of Porsche SE, Wendelin Wiedeking, and his former finance chief, Holger Haerter, with market manipulation of VW shares during Porsche SE's botched 2008-09 takeover attempt of much larger VW.
Prosecutors in Stuttgart, where Porsche SE is based, have been investigating since 2009 whether the company misled investors in 2008 when it claimed it had no plan to acquire VW.
Porsche SE has repeatedly denied the allegations.
Some German and U.S. investors say that throughout 2008 Porsche SE camouflaged its plans to buy VW and secretly piled up its holding.
In March 2008, Porsche SE dismissed as "speculation" talk that it intended to take over VW.
Seven months later, Porsche SE said it controlled 42.6 percent of VW's common shares and held options for another 31.5 percent of the stock it had not disclosed previously.
Porsche SE's statement caused VW shares to surge to 1,005 euros within days, briefly making VW the world's most valuable company as short-sellers raced to buy back stock they had borrowed to bet that VW shares would drop.
Porsche SE's attempts to buy VW backfired and pushed it to near bankruptcy. Instead of buying VW, the company ended up selling its sports car business, Porsche AG, to VW.
($1 = 0.7474 euros) (Reporting by Hendrick Sackmann; Writing by Andreas Cremer; Editing by Mark Potter)