Volkswagen is Europe's biggest carmaker
Volkswagen's share price has more than doubled after sports car maker Porsche announced at the weekend that it had increased its stake in the company.
At close of trade in Frankfurt, VW's shares were up 146.6%, or 309.15 euros, at 486.45 euros.
Porsche said on Sunday it had lifted its stake in VW to 42.6% and intended to increase this to 75% in 2009.
The announcement led to a surge in VW's share price as investors scrambled for the remaining VW shares on the market.
In its announcement on Sunday, Porsche reiterated its intention to increase its stake in VW above 50% by the end of the year.
It also announced that it had options to buy an additional 31.5% of VW.
The news led to VW's share price rocketing, as investors who had sold VW shares hoping to buy them back later at a lower price - known as short-selling - sought to lay their hands on VW stock.