T.I. Back in Federal Custody

After only a day in the semi-real world following months in prison, T.I. is already back in federal custody.

The Federal Bureau of Prisons confirms to TMZ that the rapper checked into a federal penitentiary in Atlanta last night, but would not elaborate further.

According to T.I.'s lawyer, Steve Sadow, he's back in federal custody because of an issue involving his trip from the Arkansas prison to his Atlanta halfway house on a luxury bus on Wednesday.

Sadow tells TMZ, "We are awaiting the opportunity to quickly resolve whatever the issue may be that the Federal Bureau of Prisons has with T.I.'s method of transportation, bus, from Arkansas to Atlanta, so that T.I. can return to the halfway house to complete the remaining days of his sentence."

Sadow adds the issue was not drug-related.

T.I. was sentenced in October to 11 months in prison for violating his probation, but was let out early. He was to complete the rest of his sentence in the halfway house.

Story developing ...

5:55 AM: TMZ spoke with T.I.'s uncle, who reiterated to us ... T.I. was not drinking on the bus to Atlanta and showed up to the halfway house sober and on time. The uncle says T.I. "stopped drinking a long time ago."