The man, identified as Alessandro Bassi, died in Rubbiano di Solignano, near the northern city of Parma.
A source familiar with an investigation into a multi-billion-euro accounting hole at Parmalat said Bassi worked with two former finance directors of the food group, Fausto Tonna and Luciano Del Soldato.
Bassi had been questioned this week, but was not one of at least 25 people being investigated. Prosecutor Vincenzo Picciotti said Bassi had not been linked to wrongdoings.
"He was in position to give details useful for the investigation," Picciotti said. Bassi, in his 40s and married with two children, had not been due to be questioned again.
In a note, Parmalat's administrator Enrico Bondi said he and the firm expressed their deep condolences to the family, who told reporters Bassi had been "distressed" by the scandal.
Parmalat founder questioned
A financial scandal has engulfed
the Italian food firm
Meanwhile, prosecutors questioned Parmalat founder Calisto Tanzi in hospital on Friday.
Tanzi was taken from a Milan prison to the emergency room of a city hospital on Thursday after feeling tingling sensations that could be symptoms of cardiac problems, defence lawyer Fabio Belloni said.
The former Parmalat chief was detained last month on a Milan street, and prosecutors have accused him of masterminding a web of fraud, market rigging and false accounting.
Tanzi is among 11 people arrested in the probe. He was taken to Milan's San Vittore jail on 27 December and was moved to a clinic inside the prison earlier this month.
Now 65, Tanzi previously had a heart by-pass operation.
Belloni said his client, who on Friday was in the Milan hospital's neurosurgery wing, was "alternating between moments of calm and deep anxiety" but still wanted to be questioned.
Judges have rejected requests for Tanzi to be moved to house arrest on the grounds he might flee or tamper with evidence.
Tanzi has admitted to prosecutors that he diverted about 500 million euros from publicly listed Parmalat and that the hole in its accounts might be about eight billion euros.
Tanzi oversaw the expansion of Parmalat from a single milk plant in 1961 to becoming a globe-spanning foods group.
Magistrates in Milan and Parma are trying to work out how Tanzi and others at Parmalat might have hidden for over a decade an accounting hole that investigators say could now exceed 10 billion euros.
In another development, police in Milan searched the offices of Deutsche Bank, one of several banks that sold billions of euros in bonds for food giant Parmalat.
"We will continue to fully cooperate with Italian authorities," a spokesman for Germany's biggest bank said.
Tax police have launched a
Friday's swoop by finance police came after similar searches this week in Milan of the offices of US bank Morgan Stanley , a unit of Italy's biggest bank Banca Intesa, and ratings agency Standard & Poor's.
Earlier this month the offices of Bank of America were searched and documents were taken from Citigroup.
One of the prosecutors leading the probe, Francesco Greco, said on Friday no banks were officially under investigation.
Investigations have also been launched in the United States, Luxembourg, Brazil and the Cayman Islands.
Tens of thousands of Italians have complained to authorities that their investments, worth billions of euros, were all but wiped out by Parmalat's plunge into insolvency.
Prime Minister Silvio Berlusconi's government has started drawing up regulatory reforms, and his cabinet is discussing ways to protect investors.