SAN DIEGO -- Randy "Duke" Cunningham is back in San Diego on Tuesday -- under lock and key.

The ex-congressman sentenced to prison for taking millions in bribes from defense contractors arrived at the federal lockup in downtown San Diego on Sunday night in an orange jumpsuit was put in a segregated unit.

Cunningham was brought to San Diego from a federal prison in Tucson, Ariz., for follow-up interviews with federal prosecutors, The San Diego Union-Tribune reported.

Prosecutors are preparing for the trials of Cunningham's alleged co-conspirators: Poway defense contractor Brent Wilkes, former CIA official Kyle "Dusty" Foggo and New York mortgage broker John Michael.

Cunningham is expected to remain in San Diego until prosecutors are certain they no longer need his help to prepare for the trials, federal law enforcement sources told the Union-Tribune.

His presence should not be interpreted to mean he has cooperated enough to earn a reduction in his sentence, sources told the newspaper.

Wilkes and Foggo have pleaded not guilty to conspiracy, honest services wire fraud and money laundering charges contained in an indictment.

Michael is charged with obstruction of justice. He and Wilkes are expected to stand trial Sept. 18 on charges contained in a separate indictment.

Wilkes provided more than $700,000 to Cunningham, who in return betrayed the public trust by corruptly influencing the appropriations of funds and the execution of government contracts that would help Wilkes' company, ADCS Inc.

Cunningham began his eight-year prison term last year.