Senate Democratic leaders, through their spokeswoman, said they were aware of the search.
"The Senate Democratic caucus, its members and staff, will fully comply and cooperate with any request made by the attorney general," Senate Democratic spokeswoman Stacey Witalec said in an e-mailed statement.
Washington was first elected to the legislature in 1993 and served 12 years in the state House of Representatives before being elected to the Senate in 2005. Her district includes northwestern Philadelphia and pockets of Montgomery County, and she serves on four committees, including Aging and Youth, where she is the ranking Democrat. A survivor of domestic violence, she is known for her advocacy against domestic violence, abuse, and rape, and in recent years, she has worked to strengthen child-abuse prevention laws.
Friday's search of Washington's offices does not appear to be related to any other investigation, according to the sources. No other legislative offices were searched, they said.
Investigators typically ask a judge to approve a search warrant to get documents or evidence they suspect will not be surrendered voluntarily or could be destroyed.
It would not be the first time the Attorney General's Office has probed legislators' use of taxpayer resources for political purposes.
In 2007, Gov. Corbett, then state attorney general, began investigating millions of dollars in taxpayer-funded bonuses paid to legislative staffers for political work. The probe came to be known as Bonusgate and spawned several offshoot investigations that landed some of Pennsylvania's top elected officials behind bars, including onetime House speakers John M. Perzel, a Republican from Philadelphia, and Bill DeWeese, a Democrat from Greene County.
Perzel pleaded guilty to charges that he used state money to buy expensive and sophisticated computer programs used to help Republicans win political campaigns. DeWeese was convicted last year on charges that he directed legislative staffers to do campaign work on the taxpayer dime and time.
Separately, onetime Republican State Sen. Jane Orie of Allegheny County was imprisoned last year for using state employees for political purposes. That case was handled by the Allegheny County District Attorney's Office.