Former defence minister Edgar Alain Mebe Ngo'o, once tipped to succeed Cameroon President Paul Biya, has been charged with diverting public funds and corruption.
"Mr Mebe Ngo'o is suspected of diverting public money and corruption," an official of the Special Criminal Tribunal told the French news agency, AFP.
Mebe Ngo'o was put in provisional detention on Friday and sent to the central prison in the capital Yaounde, the official added.
"He was locked up along with the deputy director of a bank, a Treasury inspector and an army colonel," he said.
A fifth person was still being questioned in the same investigation.
The former minister was summoned Tuesday to the tribunal, which deals with major corruption cases, and detained.
Mebe Ngo'o was sacked from the government last year where he served from 2015 as transport minister after spending the six previous years at defence.
Cameroonian journalist Jules Koum Koum, who died in a road accident, had in 2010 investigated an alleged over-billing scandal for military uniforms at the defence ministry when Mebe Ngo'o was minister.
Before joining the government, he had led the police force and run the presidency's civil office.