Brown, a former mayoral candidate and former employee of the Department of Health Care Finance, says he was paid cash and promised a job by the Gray campaign to launch verbal attacks against then Mayor Adrian Fenty during the race.
The probe is being led by Rep. Darrell Issa (R-Calif.), who chairs the House Oversight and Government Reform Committee.
Issa says because his investigators have essentially been stonewalled in their attempts to interview key figures close to Gray, he has lost confidence in the District government's ability to probe what happened.
There are several investigations already underway. The Office of Campaign Finance is conducting an audit and the U.S. Attorney's office and FBI say they're working together to assess the allegations.
A spokesperson for the House Oversight and Government Reform Committee says a hearing date has not been set.
Gray, in a statement, says that while he will cooperate fully with the House probe, he doesn't believe congressional involvement will illuminate any additional issues or information.