Parmalat Finanziaria, the Italian dairy and food giant, engaged in a tangled scheme involving dozens of offshore front companies to invent assets that offset as much as $11 billion in liabilitiesover more than a decade, Italian investigators said Tuesday.

The crisis at Parmalat, with its eerie echoes of the Byzantine partnerships that contributed to the collapse of Enron in the United States, dwarfs all other accounting scandals in Europe in recent years and raises questions about the ability of European regulators to oversee their global and increasingly financially sophisticated companies.

The debacle prompted the government in Rome to pass a decree on Tuesday to make it easier for Parmalat to reorganize while enjoying protection from its creditors. On Tuesday evening, Parmalat’s board met and agreed to embrace the government decree affording immediate protection from creditors. But a person close to the board said it could not formally accept the decree’s provisions until Wednesday, when the decree officially takes effect.

While the investigation is still in its early stages and many questions remain, we have a rough outline, said Francesco Greco, the chief investigating magistrate.

The seeds for Parmalat’s downfall appears to have been sown at the end of the 1980’s, when the company was preparing to sell shares to the public for the first time, people close to the investigation said. Calisto Tanzi had taken his family hams and preserves, and, over several decades, turned them into a global milk and food powerhouse, selling products like Archway cookies, Pomi tomato paste and its long-life milk in 30 countries, including the United States. The Tanzi family was looking to cash in on some of that remarkable growth. At that time, Parmalat started creating finance companies in the Antilles, essentially to dump liabilities that it then offset, at least on paper, with assets it simply invented, people close to the investigation said. The Tanzi family still holds 51 percent of Parmalat.

At the time, the Parmalat group, including the offshore finance companies, was audited by the accounting firm Grant Thornton. In the mid-1990’s, Italy introduced sweeping overhaul of its financial system that required Italian companies to rotate their auditors every nine years. So in 1999, Parmalat brought in Deloitte & Touche to replace Grant Thornton.

Before doing so, however, Parmalat effectively closed down the Antilles-based companies, replacing them with Bonlat, which was registered in the Cayman Islands. Yet while Deloitte assumed responsibility for the Parmalat group, the auditing of Bonlat remained in the hands of Grant Thornton.

Parmalat, in information it has provided for investors, describes Bonlat as a treasury center. But people close to the investigations called it a garbage can, where Parmalat parked all manner of liabilities accrued at its various subsidiaries around the world.

Magistrates here in Milan, Italy’s financial capital, spent all day Tuesday questioning Fausto Tonna, one of roughly 20 current and former Parmalat executives and others who are under investigation for possible fraud. Tonna, who was chief financial officer for 16 years before he resigned in February, was a principal architect of Parmalat’s tangled financial structure. He was also a director of Bonlat Financing.

On its balance sheet, Parmalat declared Bonlat to be in possession of assets that included the 3.95 billion, or $4.9 billion, supposedly held by Bank of America. In fact, Bonlat’s assets appear to have been nonexistent, appearing only on paper, the people said.

Investigators said that despite intense questioning of company officials and the advisers, many questions remained unanswered. On Monday, Greco and his team spent the day questioning Gian Paolo Zini, an Italian lawyer and adviser to Tanzi. But they said it remained unclear when exactly Parmalat allegedly developed the offshore scheme for offsetting liabilities with fictitious assets and which liabilities it originally included in the scheme. Nor is it clear who dreamed up the scheme.

Zini was heard as a witness, while Tanzi, Tonna, and two other former chief financial officers, Luciano Del Soldato and Alberto Ferraris, are among those under investigation for possible crimes. Moreover, investigators want to know why Parmalat was so frenzied in its invention of assets, whether to mask immense losses in what was often considered a relatively profitable company, because assets were being stolen, or for some other reason or combination of reasons.

Investigators have also been trying to determine whether Parmalat repurchased 2.9 billion of bonds that it claimed to have done in its reporting. People close to the investigation said Tonna said that it had not.

If the bonds were not bought back, that would bring Parmalat’s total debt to 8.9 billion, compared with 6 billion it reported at the end of September.

Investigators appear also to have succeeded in identifying only about $1.4 million in assets in Epicurum, a hedge fund based in the Cayman Islands from which Parmalat said earlier this month that it expected a payment of $589.9 million on Dec. 4. Failure to obtain that money resulted in Parmalat making late repayment of a bond of 150 million that came due in December.

People close to the investigation suggested that certain elements, including the retention of Grant Thornton as Bonlat’s auditors after the 1999 rotation, appeared to point to the possibility that auditors at Grant Thornton knew of Bonlat’s fictitious assets.

A spokeswoman for Grant Thornton in London said the firm was cooperating with the investigation. The spokeswoman, Nan Williams, said she could not confirm that Grant Thornton was the principal auditor for the Parmalat group before 1999. She emphasized that Grant Thornton was partly responsible for the current investigation because it wrote last December to Bank of America seeking confirmation of the Bonlat account at the bank.

In March, Parmalat sent Grant Thornton documents on Bank of America letterheads confirming the accounts. Bank of America subsequently declared the letters forgeries.

In a statement later Tuesday, Grant Thornton insisted the Bonlat audit was conducted in full compliance with appropriate, current auditing standards, but acknowledged that the firm may have been the victim of a fraud committed by others. It said it continued to audit about 17 Parmalat subsidiaries, of a total of roughly 200.

People close to the investigation said the documents had been forged using scanners, probably by Parmalat finance officers, though they did not identify them. Bank of America denied Tuesday any involvement and said it had filed a criminal complaint with the investigating magistrates. A bank spokeswoman said the complaint related to possible forgery.