Update: 8:50 p.m.

The Justice Department released documents today detailing how officials prepared a Feb. 4 letter to Sen. Chuck Grassley (R-Iowa) that Attorney General Eric Holder has since admitted contained false information about Operation Fast and Furious, a botched gun operation under investigation by Congress.

The documents show that Dennis Burke, then a U.S. attorney who has since resigned, and William Hoover, then the deputy director of the Bureau of Alcohol, Tobacco, Firearms and Explosives who has since been reassigned, principally provided the false information to officials who drafted the letter. But the documents do not shed light on whether either knew the information was false at the time.

In the Feb. 4 letter, Assistant Attorney General Ronald Weich broadly denied that ATF officials had allowed assault weapons to “walk,” which meant ending surveillance on weapons suspected to be en route to Mexican drug cartels, allowing the guns to escape into the wild. “ATF makes every effort to interdict weapons that have been purchased illegally and prevent their transportation to Mexico,” Weich wrote.

Grassley’s allegations about Fast and Furious, later revealed to be true, “are based on categorical falsehoods,” Burke wrote in a Jan. 31 email. Faith Burton, a Justice Department official who drafted an early version of the letter, took notes based on a phone conversation with Hoover that read, “ATF doesn’t let guns walk.”