It started when two members asked for the information and were turned down by the bureau, which cited concerns about possible leaks.
Now 33 members of Congress are demanding that the FBI provide an update on their investigation of the anthrax attacks that killed two U.S. Postal Workers from suburban Maryland and shut down the Hart Senate Office Building for several months more than five years ago.
The lawmakers sent a letter on Tuesday asking Attorney General Alberto Gonzales for a briefing, saying "it's unbelievable" that members of Congress, including some who were targets, "haven't been briefed for years" on "one of the most important terror investigations ever undertaken by the FBI," CBS News Capitol Hill correspondent Sharyl Attkisson reports.
"The FBI's refusal to brief Congress on this matter is unprecedented and inexcusable," said Rep. Rush Holt, D-N.J.
Both Republicans and Democrats signed the letter, including Sen. Patrick Leahy, D-Vt., who was among the targets of the 2001 anthrax attacks. He had an anthrax-filled letter sent to his office.
A photo editor in Boca Raton, Fla., died that same year after being exposed to anthrax in an envelope mailed to the building.