The members of Rajapaksa's immediate family and others are charged of money laundering. His second son Yoshitha Rajapaksa, who is also a navy lieutenant is currently in remand custody over money laundering charges. He was arrested on January 30 last month.
Rajapaksa's younger brother Basil Rajapaksa, the former economic development minister has also been charged in court in addition to facing the special presidential panel probing corruption.
The opposition has accused the government of a political witch hunt by targeting the members of the former regime.
Yoshitha was quizzed in connection with TV channel Carlton Sports Network (CSN) which had close links with the Rajapaksa sons.
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CSN was controversially handed over Sri Lankan cricket's television broadcast rights under the Rajapaksa regime. The broadcast rights had been the preserve of the state television until then.
Nishantha Ranatunga, who was CSN's CEO, was also among those arrested. He was also the Secretary of the Cricket governing body.
Wickremesinghe said that the investigators must be given time to conduct a comprehensive probe.
On the question of alleged off shore accounts maintained by the members of the former regime, Wickremesinghe said no police complaints have not been lodged over offshore accounts as part of the corruption probe.
Action on off shore accounts will be taken when details of them transpired through the on going investigations.