BERLIN: Anti-corruption officers have searched the homes and offices of two former Porsche chiefs and not only the German automaker's headquarters, news magazine Der Spiegel reported.

The company had said Thursday prosecutors with search warrants raided the headquarters of the luxury carmaker and opened a probe against former chief executive Wendelin Wiedeking on insider trading charges.

Quoting a spokeswoman for the Stuttgart prosecutor Der Spiegel said in its issue to be published Monday that the private apartments of Wiedeking and former financial director Holger Haerter had also been searched.

It did not say when the searches were carried out.

Wiedeking resigned as Porsche's chief executive officer last month after failing in his bid to acquire Volkswagen, Europe's biggest carmaker. Haerter stepped down at the same time.

Die Welt newspaper said the probe by Stuttgart prosecutors was linked to information provided by German banking regulator BaFin after Volkswagen shares soared last October, following reports of its expected acquisition by Porsche.

The project ultimately fell through.

During the Porsche/VW takeover saga, a series of so-called cash settlement options in VW shares earned Porsche billions as the stock climbed in value and were at one point quoted at more than 1,000 euros a share.

That briefly made VW the world's biggest company by market capitalisation.

VW was quoted at 151.47 euros at the market's close on Friday.

Der Spiegel said however that the latest investigation was not focussing on the share's October 2008 boom but on the fact that Porsche allegedly tried "with help from Frankfurt's Maple Bank to stabilise the VW share at a certain level to stop the share price from again fluctuating dangerously".

Such fluctuations could have led to massive losses for Porsche which at the time held more than half of VW's shares as well as options, Der Spiegel said.

Under Wiedeking, Porsche built up a 51-percent stake in the much larger VW and wanted to take full control but the attempt failed and left Porsche squeezed under a huge debt pile. The two firms now plan to merge by 2011 and to overtake Japan's Toyota to become the world's biggest car company by 2018.