If convicted, they face up to eight years in jail.
Serbia has come under pressure from Nato and the EU to capture Mladic and have him extradited for trial at The Hague for atrocities committed during the 1992-95 Bosnian war.
The charges against Mladic include his alleged responsibility for the 1995 massacre of up to 8,000 Muslims in the east Bosnian town of Srebrenica during the war.
The EU has suspended pre-entry talks with Serbia until Mladic is found.
The same condition was imposed by Nato regarding Serbia's aspirations to join the alliance, but the Balkan country was recently allowed into a Nato outreach program.
Carla Del Ponte, prosecutor for the International Criminal Tribunal for the former Yugoslavia, told Al Jazeera she believed Belgrade knew exactly where Mladic was.
"I hope the international community will keep strong pressure on Belgrade," she said.
The trial of those alleged to have helped Mladic began in September and continued on Monday.