Interior Ministry officials say the presidium will deliver a report on the officers in question, including their names, ranks and positions. But beyond that, the ministry is keeping details of the investigation quiet, and did not say when any report would be ready.

"Prior to forwarding our report to [Interior Minister Ivan Langer], we do not wish to make any comments on this issue," Police spokesman Pavel Hanták said Sept. 29.

Langer made public the existence of former StB officers in the Police Presidium Sept. 26, and said they should leave the force.

Last year, Langer, then the shadow interior minister for the Civic Democrats (ODS), made similar charges, which the ruling Social Democrats (ČSSD) largely ignored.

Now opponents of Langer, mostly from the ČSSD, say it would be wrong to sack the officers, since it has been 17 years since the fall of communism.

The presidium first answered Langer's charges in the press by saying it did not have exact records of the number of former StB agents currently working as police officers.

"That's unlikely," said Pavel Žáček, an StB historian at the Czech Academy of Sciences. "The presidium's register gives a list of all units that officers served in. The data have to be available."

The controversy comes at a time when the presidium's ranks are on the decline. Last year, nearly 2,800 officers left the force in reaction to, among other things, a new civil service law that changed the structure of pensions and benefits they receive.

If even more leave after being exposed as former agents, the city could find itself doing mass hiring. Prague Mayor Pavel Bém recently issued a call for more police on Prague streets as a deterrent to crime.

The question remains why it has taken so long for the interior minister to address the issue of police with communist pasts.

After the 1989 revolution, a system was put in place that vetted public offices for workers who had roles in the past regime. Žáček said police escaped scrutiny.

"The fact is that there was simply nobody to replace them at the time," he said.