Staff of the state anti-corruption bureau took Bakili Muluzi to their office in the commercial capital, Blantyre, for more than an hour of questioning before releasing him, his lawyers said.
Sam Mpasu, his spokesman, said Muluzi faced six corruption charges in connection with allegations that he diverted large sums of money from donors into his personal bank account.
A defence lawyer said: "The former president denies all the charges, and he has invoked his constitutional right to remain silent.
"Since the anti-corruption bureau has already made a decision to take him to court, Dr Muluzi found no reason to furnish them with any statement."
Muluzi says that he is a victim of "political persecution" because of a long-running feud with his successor, Bingu wa Mutharika.
Wa Mutharika quit Muluzi's United Democratic Front party last year, accusing his former allies of blocking his clampdown on corruption, and survived a subsequent attempt to impeach him.
Money raised by selling grain
reserves has never been found
Several former government officials are either being investigated or are on trial for fraud and corruption.
Muluzi was hailed as a hero in Malawi after removing Hastings Kamuzu Banda, the veteran independence leader, in 1994.
During his second term as president, the International Monetary Fund, World Bank, the US and the European Union withheld nearly $100 million from the government because of poor economic policies and corruption.
Under Muluzi, Malawi's maize reserves were sold to other countries shortly before a drought that caused widespread famine. Despite international pressure, the millions of dollars raised from the sale of food reserves have never been found.
Malawi is one of the world's poorest countries - corruption and the unsettled political situation meant that donors were reluctant to add it to the list of countries eligible for debt relief.
The World Bank and IMF are expected to cancel about $2.9 billion of the country's external debt in September.