The four high-profile police officers arrested on drug charges will remain behind bars until the conclusion of their trial.
A Roodepoort magistrate agreed with the prosecution that the men might tamper with witnesses. She denied them bail.
The four officers, the West Rand organised crime unit's head Senior Superintendent Dumisani Jwara and captains Landro Mokgosani, Chaiphus Shange and Victor Juili, appeared before magistrate Delise Smit.
Lawyers representing the men but indicated they would go back to the drawing board and prepare fresh presentations for another bail bid in a senior court.
Ruling against bail, Smit said: "It is disturbing to this court that the state said the case was top secret - but the applicants knew about it. The accused have strong bases to get information. They have people who are well positioned. They knew about their warrants of arrest being issued while the commander didn't know.
"This is a serious case and a long imprisonment term could be passed if they are found guilty. The threats made to the investigating officer are very serious. Bail is therefore denied."
Smit read out a paragraph from Jwara's statement: "I recall saying we are all officers carrying guns and had similar training, and that they should be careful because we could investigate them ."
Smit said these threats were made during an identity parade, and showed that the witnesses were under threat.
The four will be detained at the Johannesburg Central police station's high risk facility until their next appearance in June.