Former Zambian president Rupiah Banda appeared before an official investigation panel on Monday to answer allegations of corruption during his three years in charge of Africa’s biggest copper producer.

Police barricaded roads leading to the national anti-drugs offices, where Banda underwent more than two hours of questioning behind closed doors before the session adjourned until Tuesday.

After his release, Banda, who was stripped of his immunity from prosecution last week, urged supporters gathered outside the building not to try to take the law into their own hands.

“May I ask you all to remain calm even under extreme provocation. This is our country,” he said.

Defense lawyer Robert Amsterdam has accused President Michael Sata’s government of launching a witch hunt against Banda, who ruled the southern African country from 2008 to 2011, when he lost an election to Sata.

Since then, a few Banda officials have been convicted in high-profile corruption probes into deals struck during his time in office, and prosecutors are continuing to investigate suspected shortfalls in state revenues from copper mining.

In February, Banda, who then enjoyed immunity from prosecution, was summoned for questioning but refused to appear before the panel.