The following is breaking news from FOX News Channel's Washington, D.C. bureau:

14:50 p.m. EDT A very senior source who has seen the latest batch of documents to be delivered to the Senate says Sen. Chuck Schumer is wrong in estimating that the Department of Justice will dump about 1,00 pages related to the U.S. attorney firings sometime between 4 and 5 p.m. EDT.

As the afternoon drags on, it is looking more likely that the dump will slip to either very late Thursday or Friday.

In a press conference earlier in the day, Schumer said he is looking for unredacted versions of memos, e-mails and other pages previously released by the department, and specifically, a document that contains performance rankings for all U.S. attorneys.

09:22 a.m. EDT Kyle Sampson, former chief of staff to Attorney General Alberto Gonzales, will return to Capitol Hill on Friday for a voluntary follow-up interview with House and Senate staffers investigating the firings of eight U.S. attorneys, a source with knowledge of the congressional investigation told FOX News on Wednesday.

The source said Sampson, who testified late last month on the firings, is committed to cooperating fully with the congressional investigation and "despite his lengthy public testimony, has agreed to make himself available again to ensure that any outstanding questions are answered."

FOX News' Ian McCaleb and Trish Turner contributed to this report.