Investigative magistrates are threatening to stage a direct confrontation between two of the alleged masterminds behind the Parmalat scandal this week in an attempt to trace €10 billion estimated to have disappeared from the bankrupt dairy group.

Investigators in Parma yesterday subjected Mr Fausto Tonna, Parmalat's veteran chief financial officer, to a grilling.

They are expected today to turn to Mr Gian Paolo Zini, Parmalat's chief legal counsel who helped set up many of the foreign and offshore companies now under scrutiny.

If there are discrepancies between their separate testimonies, magistrates are expected to organise a direct confrontation between the men. Both were arrested last week.

Mr Tonna appeared in no mood to co-operate when he arrived for interrogation yesterday. He turned to journalists to say: "I wish you and your families a slow and painful death." Later, according to court sources, he said he was only executing orders given him by Mr Calisto Tanzi, Parmalat's founder and chairman until he was removed from office three weeks ago. Mr Zini also denied wrongdoing.

Investigators in Milan, meanwhile, are expected to dig further into the roles played by Bank of America and Citigroup in Parmalat's web of offshore companies. Citigroup took a minority stake when Parmalat set up an offshore company called Buconero, "black hole" in Italian, used to make inter-company loans that were kept off Parmalat's balance sheet.

Magistrates are particularly interested in how Bank of America organised the acquisition of an 18 per cent stake in Parmalat's Brazilian unit in 1999 for two generically named investment groups, Food Holdings and Dairy Holdings.

According to people familiar with the transaction, investment bank Salomon Smith Barney had found investors ready to buy a stake in the unit only to be turned away by Mr Tonna.