His lawyers and family say they have been unable to trace him despite making inquiries at several police stations, including the Police headquarters in Naguru. Security agencies had not publicly confirmed his detention or disclosed where he is being held by the time of publication.
Kivumbi was reportedly rearrested in Mpigi Town Council shortly after securing temporary release on bail from the High Court.
Witnesses said heavily armed operatives dressed in police uniforms, military fatigues and civilian clothing intercepted his vehicle, forcibly removed him and bundled him into a waiting "drone" van, which drove to an undisclosed location.
His lawyers and relatives said all efforts to locate him have so far proved unsuccessful.
"We searched the police in Mpigi, along the highway up to the Police headquarters, and they have denied arresting Kivumbi," said one of his lawyers, Samuel Muyizzi.
Muyizzi said the legal team had received unverified reports that the vehicles involved in the arrest were later seen in Mbuya, fuelling speculation that Kivumbi may have been taken to a military facility.
"Unconfirmed reports show that he was driven to Mbuya," Muyizzi said.
"But if this is true, then it's also illegal because we don't know that the military should be carrying out arrests and later detain people," he added.
Muyizzi said the defence team is awaiting an official explanation from the authorities. If none is provided by Monday, the lawyers plan to petition the High Court for a writ of habeas corpus, seeking an order compelling the government, the Uganda Police Force and the Uganda People's Defence Forces to produce Kivumbi before court and explain the legal basis of his detention.
"Our position is very simple. We shall process the necessary documents and run to court seeking a writ of habeas corpus. We want the court to compel the military, the Uganda Police and the government to produce Kivumbi and explain his detention," Muyizzi said.
Kivumbi had earlier been granted temporary bail by the High Court alongside several co-accused facing terrorism-related charges.
He has consistently denied the allegations, describing them as politically motivated.
At the time of his reported rearrest, Kivumbi was said to be working with members of the defence team to secure the release of other co-accused persons who remain on remand.
Authorities had not issued an official statement on the reported rearrest or Kivumbi's whereabouts by the time of publication.