A South African court has withdrawn charges against the man investigating police chief Jackie Selebi.
Prosecutors will serve an indictment on Mr Selebi soon
Gerrie Nel, a senior member of the Scorpions special investigations unit, was arrested by police last week on corruption charges.
Mr Selebi, who denies any wrongdoing, has been suspended from duty, and has resigned as the president of Interpol.
Prosecutors say he will be indicted on charges of corruption over his friendship with a drugs smuggler.
The BBC's Peter Biles in Johannesburg says Mr Nel, the head of the Scorpions in Gauteng Province, appeared in the dock for just a few minutes.
It was then announced that all charges against him were being dropped.
He had been arrested at his home in Pretoria last Tuesday by around 20 armed police officers.
Mr Nel's lawyer said that his client now just wanted to get back to work.
The arrest last week was widely seen as part of the fierce rivalry that exists between the Scorpions and the police - which are independent of one another.
"This whole prosecution [of Mr Nel] came from the police. So you must see a connection. There are too many things that are not just coincidence. The coincidence is just too stark," legal expert Marinus Wichers told SABC radio.
"It will deepen the rift between the Scorpions and the police, unless the change of circumstances [the suspension of Mr Selebi] is the basis for a new working relationship."
The opposition Democratic Alliance is calling for an independent inquiry into why Mr Nel was arrested by the police last week.
The National Prosecuting Authority says it will charge Mr Selebi with corruption and "defeating the ends of justice".
An indictment is expected to be served on him soon.
He is alleged to have received $170,000 (£90,000) from a convicted criminal.
South Africa's chief prosecutor alleges that Mr Selebi had a "generally corrupt relationship" with businessman Glen Agliotti - a convicted drug smuggler who is also accused of involvement in the 2005 murder of mining magnate Brett Kebble.
Mr Selebi is said to be close to South Africa's President Thabo Mbeki, who has resisted calls for his police commissioner to be fired.
He said he would not take any action until evidence of Mr Selebi's wrongdoing was brought before him.
But on Saturday he put Mr Selebi on an extended leave of absence.
Mr Selebi was elected president of Interpol for a four-year term in 2004.