A close aide of Slobodan Milosevic is being questioned in Belgrade about an apparent attempt to assassinate former opposition leader Vuk Draskovic.
Former secret service chief Rade Markovic was arrested last Friday in connection with the incident in October 1999 in which four other people were killed.
Markovic denies any role in the apparently staged car crash that left Mr Draskovic, at that time the prime opponent of Milosevic, slightly injured.
Markovic is being held in the Central Prison in Belgrade, along with several other Serbian police officers - his close associates - who were arrested with him, Belgrade court sources said.
Milosevic and his influential wife Mirjana Markovic were believed to be behind the Serbian secret service's alleged links to a string of unsolved murders and human rights abuses during his 13-year rule.
Serbian Interior Minister Dusan Mihajlovic said on Sunday that Milosevic was being investigated on a number of charges. One of the first that could bring Milosevic to justice are his allegedly false statements about his assets.
Mr Mihajlovic said Milosevic was given a house toward the end of his 13 years in power in the upscale Dedinje district after signing documents that gave a false picture about his assets.
If tried and convicted for lying about his assets to secure the house, Milosevic could be sentenced to up to three years in prison, Mr Mihajlovic said.