Congress is set to hold hearings into the General Service Administration spending scandal this week.
The GSA has been under fire from Congress for spending more than $820,000 in taxpayer money at a conference in Las Vegas in 2010.
The House Committee on Oversight and Government Reform will conduct the initial hearing on Monday. Lawmakers are expected to look well beyond the conference for more evidence of wasteful spending.
One GSA executive who is the focus of the investigation, Jeffrey Neely, has refused to testify voluntarily and has been subpoenaed to appear at Monday's hearing. Neely's lawyer said the witness will assert his constitutional privilege to remain silent.
Internal GSA memos, obtained by committees from GSA inspector general Brian Miller, indicate that lavish spending was part of a pattern and became the subject of insider jokes among GSA employees.
One employee even bragged about the conference spending in a rap video that won a prize at the event.
Another employee told internal investigators that agency executives kept scheduling award ceremonies to justify giving employees free food at GSA events away from the office.
By having the food connected to a ceremony, employees did not have to pay for the meals with their daily expense allowance. But taxpayers picked up the tab.
GSA administrator Martha Johnson has resigned in the wake of the scandal. Eight GSA employees have been placed on administrative leave.
An internal government memo released Friday shows officials of the GSA were aware of a spending problem months before the scandal broke.
The GSA is the agency that creates conference guidelines for other federal agencies.