Vitter tried to keep a low profile Tuesday on Capitol Hill.
WASHINGTON (CNN) - Sen. David Vitter returned from a week-long absence from Congress Tuesday, a day after he made a public apology for "a serious sin" as investigators probe an alleged prostitution ring that operated in the nation's capital.
Vitter, a conservative Republican, last week vanished from public view after his phone number turned up among those kept by a reputed "DC Madam" in records that have become part of her upcoming criminal trial.
Tuesday morning, Vitter did not visit his Senate office, where the media had camped out in anticipation of his return. He also was not seen at a residential address near the Supreme Court building.
He eventually emerged at a scheduled Senate hearing taking place near his office building. He arrived nearly 30 minutes late for the start of the panel, which heard testimony regarding commercial airline service to outlying parts of the U.S.
At first, only CNN and a local camera crew had learned of his whereabouts. But as word spread among media outlets, Senate officials had to urge order among the gaggle of newspaper writers, photographers and other television crews which began making noisy entrances to record Vitter's return.
The senator left the hearing early, and tried to ignore shouted questions and camera lights in the hallway. He then turned and stopped.
Vitter referred to comments he made Monday evening in his hometown, then said, "I look forward today to be back at work, really focused on a lot of important issues for the people of Louisiana. I'll leave it at that."
Vitter apologized privately to his fellow Republican senators at their weekly policy lunch Tuesday, senators who attended the lunch said.
One senator described his apology as "humble" and "short and to the point." The senator said Vitter was met with a great deal of "empathy" by the senators in the room.
- CNN's Paul Courson and Ted Barrett