Zambia's ex-President Rupiah Banda has appeared before an official panel to answer allegations of corruption during his three year in power.
Police barricaded roads leading to the national anti-drugs offices in the capital Lusaka, where Mr Banda was questioned for more than two hours behind closed doors, reports say.
Zambia's parliament stripped him of his immunity from prosecution on Friday.
Mr Banda's lawyer, Robert Amsterdam, says he is the victim of a witch hunt.
He stepped down from office in 2011 after losing elections to President Michael Sata.
He was widely praised for accepting defeat, rather than challenging the result.
Last June, his eldest son, Andrew Banda, was charged with corruption following allegations that he took a 2% cut from all road-building contracts awarded to an Italian company during his father's rule.
He strongly denied the allegation.
The ex-president's immunity was lifted after he refused to appear before the panel last month.
Mr Banda waved to supporters as he walked into the national anti-drugs offices, but did not address them, Reuters news agency reports.
After he left, a government spokeswoman said the questioning would resume on Tuesday, Reuters adds.
President Sata has launched an anti-corruption drive since coming to power that has seen a number of former ministers investigated and some arrested.