Geneva ? Adecco’s chief financial officer and the head of its U.S. operations lost their jobs Friday in an accounting scandal that the company, the world’s largest employment agency, reveals has been spurred by whistleblowers.

The company’s shares tumbled again as Adecco announced the resignation of its chief financial officer, Felix Weber, and the head of its U.S. operations, Julio Arrieta.

Adecco said it was investigating allegations made by “whistleblowers” in the United States, but gave no details. It said the accounting weaknesses under investigation in its U.S. operations included a string of problems with payroll, client billing and the security of computer systems.

Analysts said they expected Adecco — which on Monday disclosed it was looking into accounting and other problems — would have to restate its earnings for the first three quarters of 2003.

“The good news is that the problems are only in North America and some other countries which are less than 10 percent of revenues. The bad news is that the problems there are severe,” said analyst Ronald Wildmann, of Bank Leu, in Zurich.

Adecco shares fell $1.83, or 15 percent, to $10.35 in trading Friday on the New York Stock Exchange.

Meanwhile, the Dow Jones News Service reported Swiss regulators were investigating the possibility of insider trading by two family members tied to Jacobs AG, one of Adecco’s largest shareholders, in advance of Adecco’s announcement of the problems.

The report said Jacobs sold 79,500 shares during the first half of December and transferred more shares to members of the Jacobs family, in keeping with an inheritance agreement. The probe centers on two members of the Jacobs family that pushed to sell shares after that transfer, although they didn’t actually sell shares, Dow Jones reported, citing a person familiar with the matter.