Ahold hoped the scandal would quickly die

This is the third successive day of dramatic share plunges for Ahold, which admitted on Monday that accounting irregularities at a US subsidiary would cost it at least $500m (�317m).

Now, the firm has admitted that it is working with the US Securities and Exchange Commission to explore the affair, which concerns the way distribution unit US Foodservice accounted for its income.

In addition, Ahold faces a probe from Euronext, the stock market where its shares are listed in Amsterdam, and a possible flurry of lawsuits from disgruntled investors.

Ahold shares have now lost 74% of their value since the beginning of the week, wiping out $7bn of shareholders' money.

The scandal spreads

Ahold's chief executive and chief financial officer have resigned, and the company says it will restate its results for the past three years.

But its hopes of drawing a line under the issue seem to have come to nothing.

There are increasing concerns that the accounting problem was something more reprehensible than an honest mistake.

Although deliberate fraud has not yet been alleged, some investors allege that Ahold was less than complete in its disclosure of financial information, and that regulators were lax in their treatment of a complex international company.

There are also concerns over the transparency of the Amsterdam market, where brokers were tipping Ahold shares until the moment it released its bad news.

Under attack

Ahold has been keen to stress that the SEC inquiry is in full co-operation with the company.

Markets are nervous there could be more surprises to come, or that the company could take hasty action to dig itself out of its predicament Click here for more on Ahold's problems

Less benign, however, is a number of lawsuits, largely from investors in the US.

Two lawsuits were filed on Tuesday in Virginia and New York by law firms that have specialised in clawing back investor money after accounting scandals.

The complaints are seeking class-action status - the possibility of being rolled into one universal case that will stand as a measure for all similar suits.