FBI and Internal Revenue Service agents searched the Laurel headquarters of the Washington Suburban Sanitary Commission on Tuesday and seized documents and computer records, according to the FBI and the utility.

FBI spokeswoman Amy Thoreson said Wednesday that agents “were at the site yesterday” for several hours.

Thoreson declined to comment on the scope of the investigation because the search warrant remained sealed. She also declined to comment on whether any charges were filed as part of the investigation.

The utility provides water and sewer services to nearly 2 million people in Montgomery and Prince George’s counties.

WSSC spokesman Jim Neustadt said the utility’s police department knew about a federal investigation and was aware that a search warrant would be executed Tuesday. In a written statement, Neustadt did not provide any details of the investigation.

“WSSC has cooperated fully with the investigation,” the statement said. “Agents were given access to all documents they requested, and WSSC employees cooperated with the agents.”

A WSSC employee said FBI agents thoroughly searched two cubicles in the eighth-floor Procurement Department, which handles contracts and payments, and left with boxes of documents and downloaded computer records. The employee said the documents dated back six or seven years.

It was unclear whether the investigation is focusing on the procurement department itself, specific contracts that the utility awarded or private companies working on WSSC contracts.

Neustadt’s statement said, “WSSC has no reason to believe that the commission is a target of the investigation.”

He said he was not aware of any employees being arrested or any charges being filed. He said he could not comment on whether any WSSC employees have been disciplined in connection with the search, citing confidentiality rules about personnel issues.

Jerry N. Johnson, the WSSC’s general manager, declined an interview.

The WSSC employee, who spoke on the condition of anonymity because of not being authorized to speak publicly, said a half-dozen FBI agents dressed in suits arrived at the WSSC headquarters about 9 a.m. Tuesday and stayed until about 3:30 p.m. The agents interviewed employees in conference rooms on different floors, and word spread quickly throughout the 12-floor building as agents rode elevators between floors, the employee said.

“It caught us all off guard,” the employee said. “They had things they wanted to see, like copies of contracts. . . . No one could figure out what they were looking for.”

The employee said it appeared no one at WSSC has been placed on leave or disciplined in connection with the search. About 600 people — more than one-third of the utility’s 1,600 employees — work in the headquarters building on Sweitzer Lane, off Interstate 95, in Prince George’s.

“Everyone is talking about it,” the employee said, “but they can’t say what started it or what [the FBI] was looking for.”

A spokeswoman for Maryland U.S. Attorney Rod J. Rosenstein declined to comment.

The bicounty agency’s headquarters are on Sweitzer Lane but stand out along I-95 near Route 198 as a glistening blue high-rise in the Prince George’s suburbs.

The WSSC is overseen by a six-member board of commissioners, with three commissioners appointed by the Montgomery County executive and three by the Prince George’s executive.

WSSC leaders have been working in recent years to overcome the agency’s reputation for labor problems, political infighting and controversy surrounding how much it awarded in contracts to minority-owned businesses.

The utility’s contracting often attracts attention because so much money is at stake in contracts awarded for everything from replacing decaying pipes to designing computer systems. Last fiscal year, the WSSC awarded $816 million in contracts, a spokesman said.

Researcher Jennifer Jenkins contributed to this report.