Former Porsche executives are now under investigation over allegations they took on risks that threatened the company’s survival in a takeover battle with Volkswagen, prosecutors said yesterday.

They did not identify the executives, but Porsche’s former chief executive Wendelin Wiedeking and former chief financial officer Holger Haerter were already under investigation on allegations of market manipulation.

In addition, prosecutors said the former CFO and two other Porsche executives are under investigation for credit fraud over allegations they gave banks “false or incomplete information.’’

Porsche, the maker of the 911 and Panamera sports cars, said the investigation, begun in 2009, will be concluded at the earliest in 2012, making the planned conclusion of the merger with Volkswagen this year unlikely.

The company’s board warned that further delays would reduce the chances of a full merger altogether.

Volkswagen holds a 49.9 percent stake in Porsche.