Deputy Finance Minister Mcebisi Jonas is being investigated by the Hawks as part of a probe into allegations of corruption at state-owned South African Airways (SAA).
As part of the probe into SAA, the unit is investigating allegations that Jonas used his political influence to secure US Aircraft Company AAR Corp contracts to supply components and tyres to the state airline.
Treasury Spokeswoman Yolisa Tyantsi declined to comment.
Hawks Spokesman Hangwani Mulaudzi was quoted by City Press as saying there was an investigation into allegations of corruption at SAA, but it was policy not reveal names of those being probed.
The firm denied any wrongdoing.
Jonas has been an outspoken critic of government corruption and he opened divides within the ruling African National Congress (ANC) in 2016 when he said businessmen friends of President Jacob Zuma said they could secure him the finance ministry job.