Police in Serbia are reported to have arrested the widow of the former paramilitary leader, Arkan, in their search for the killer of Serbian Prime Minister Zoran Djindjic.
Ceca is suspected of having links with those involved in the killing
According to Serbian media, Svetlana Raznatovic - a popular singer known as Ceca - is being investigated for links to underworld figures suspected of involvement in Mr Djindjic's assassination.
Arkan, who was murdered three years ago, was reputed to be a kingpin of Serbian organised crime.
B92 radio said sources close to the Djindjic investigation believed Ceca was in contact with the gangster Milorad Lukovic, known as Legija, both before and after the assassination.
Police have already made over 300 arrests in the hunt for Mr Djindjic's assassin, and Serbia is under a state of emergency, which is expected to continue for several weeks.
Mr Djindjic was shot dead in the capital, Belgrade, last week, and the government immediately named Legija as one of the main suspects.
He was once a member of Arkan's paramilitary unit, the Tigers.
Serbian media reports said two of Ceca's security guards were also arrested when police stormed her luxury house.
Heavily armed men in camouflaged fatigues and balaclavas sealed off the house and guarded its entrances.
As the hunt for Mr Djindjic's killer continues, prisons in Serbia have been put on maximum alert.
Serbia's Justice Minister Vladan Batic said he wanted to prevent people in custody from having contact with members of their families, friends or colleagues, whether by letter, postcard or mobile phone.
Visiting rights have also been suspended.
The new measures will stay in place while the current state of emergency lasts.
The main prison in Belgrade has become so overcrowded following the recent arrests that some inmates are being transferred elsewhere.