A Chadian minister, who served as the country's premier from 2013-16 was arrested over fraud allegations, a police spokesman said.
Kalzeube Pahimi Deubet was detained on Sunday following a complaint from the state inspectorate general for fraud, the spokesperson said.
Currently secretary-general of the presidency, his post involves coordinating government action.
As well as the premiership, he has also held a number of ministerial positions.
Chad President Idriss Deby Itno, who has governed the poor, oil-rich state since 1990, last year vowed to crack down on entrenched graft.
The landlocked country has a history of political violence and corruption.
It was ranked 165th out of 180 countries in Transparency International's 2018 Corruption Perceptions Index.
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