An IT expert has been charged with hacking into Kenya's Revenue Authority and stealing $39m.
Alex Mutungi Mutuku, 28, is accused of electronic fraud but he denies any wrongdoing.
The government says there is a ring involving expatriates from the United States and other countries, along with police officers and civil servants.
A thorough background check on state employees is now being conducted, government spokesperson Eric Kiraithe told the BBC.
Other state agencies affected by the alleged hacking include the e-citizen online payment portal where users pay for government services.
Mr Mutuku was arrested after police conducted an operation following a tip-off that institutions were losing money.
A lawyer for Mr Mutuku, Tacey Makori, has asked for him to be released, arguing that police had failed to show enough evidence to warrant an extended detention.