The day before the Justice Department broadly, and falsely, denied that guns had “walked” as part of the botched “Fast and Furious” gun-smuggling operation, an agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives told supervisors in a memo that he had expressed his concerns about the operation to Congressional investigators.

In a July 3 letter to Attorney General Eric Holder, Sen. Chuck Grassley (R-Iowa) questioned whether the memo should have raised red flags at the Justice Department.

“The possibility that DOJ was aware of this memorandum on February 3, 2011, and still sent the erroneous letter to Congress on February 4, 2011, raises more questions about DOJ’s claim that faulty information from Department components inadvertently led to the false letter,” Grassley said.

The memo, from ATF Special Agent Gary Styers, documents a conversation that Styers had on July 2, 2011, with investigators from Grassley’s office.

In the memo, Styers said the operation “systematically divided and isolated agents in the group” who disagreed with the strategy of the operation.

However, Styers lists complaints about the operation that do not include allowing guns to “walk,” the tactic that has become controversial in the Fast and Furious scandal. Styers criticized the operation for its use of wiretap surveillance without a dedicated surveillance unit on the ground and questioned the experience level of the agents who participated in the operation.

In his letter, Grassley said ATF whistle-blowers have described the memo as causing alarm inside the Justice Department. However, despite the memo, the next day the DOJ sent its infamous letter denying guns had walked.

Grassley requested more information about the memo, including a list of who received it, by July 17.

A spokeswoman for the Justice Department did not immediately respond to a request for comment.