0149 GMT May 24, 2019
The source told Associated Press Sudan's public prosecutor has begun investigating Bashir on charges of money laundering and possession of large sums of foreign currency without legal grounds.
The source said military intelligence searched Bashir's home and found suitcases loaded with more than $10 million in the three currencies: $US351,000 ($490,000), six million euros ($8.38 million), and five million Sudanese pounds ($150,000).
Bashir was placed under house arrest following months of demonstrations against his rule.
He has reportedly now been moved to a high-security prison.
"The chief public prosecutor … ordered the [former] president detained and quickly questioned in preparation to put him on trial," the judicial source told Reuters.
Two of his brothers were also detained on allegations of corruption, the source said.
Bashir, who is also being sought by the International Criminal Court (ICC) over allegations of genocide in the country's western Darfur region, was ousted by the military on April 11 following months of protests.
The ex-leader's family said this week the former president had been moved from a presidential residence to Kobar prison in Khartoum.
Hassan Bashir, a professor of political science at the University of Neelain, said the measures against Bashir were intended to be a message to other figures associated with his rule that they were not above the law.
"The trial is a step that the military council wants to take to satisfy the protesters by presenting Bashir for trial," he said.
Bashir survived several armed rebellions, economic crises, and attempts by the West to turn him into a pariah during his 30-year rule before he was eventually toppled in a military coup.
Thirty-nine protesters have been killed since protests erupted in December, according to official figures. Some opposition groups say as many as 60 have died.
The Sudanese Professionals' Association, which led the latest protests, has called for Bashir and members of his administration to be held to account.
Protesters want the Military Council, which took over after toppling Bashir, to hand power to civilians.