FBI agents investigating Democratic presidential candidate Hillary Clinton’s use of a private email server knew early this month that messages recovered in a separate probe might be germane to their case, but they waited weeks before briefing FBI director James Comey, people familiar with the case told The Washington Post on Sunday.

Comey has written that he was informed of the development Thursday, and he sent a letter to legislators the next day letting them know that he thought the team should take “appropriate investigative steps designed to allow investigators to review these emails.”

That missive ignited a political firestorm less than two weeks before the election. Almost instantly, Comey came under intense criticism for his timing and for bucking the Justice Department’s guidance not to tell Congress about the development.

Given that the Clinton email team knew for weeks that it may have cause to resume its work, it is unclear why investigators did not tell Comey sooner, noted The Washington Post. People familiar with the case told the newspaper they had known about the messages since soon after New York FBI agents seized a computer related to their investigation into former congressman Anthony Weiner, who is alleged to have exchanged explicit messages with a 15-year-old girl.

Weiner is the estranged husband of longtime Clinton aide Huma Abedin, and federal law enforcement officials said they think the computer was used by both of them.

The newspaper noted that a public revelation in early October might have been less politically damaging for Clinton than one coming less than two weeks before the November 8 election. It is also unclear what agents have been doing in the intervening time and whether they were trying to learn more about the emails before notifying Comey.

An FBI spokesman declined to immediately provide a statement.

Officials familiar with the case said the messages number in the thousands and include correspondence of Abedin and Clinton.

In fact, The Wall Street Journal reported on Sunday that there were roughly 650,000 emails that would need to be examined.

The newspaper reported that it will take weeks, at a minimum, to determine whether those messages are work-related from the time Abedin served with Clinton at the State Department; how many are duplicates of emails already reviewed by the FBI; and whether they include either classified information or important new evidence in the Clinton email probe.

Abedin has told people that she is unsure how her emails could have ended up on a device she viewed as belonging to her husband, according to a person familiar with the investigation and civil litigation over the matter.

Clinton on Saturday called the new probe “deeply troubling” and urged Comey to quickly release the "full and complete facts" about the new probe of unspecified emails.