The U.S. Justice Department says it is working with the FBI to conduct the revived investigation into Hillary Clinton's emails "as expeditiously as possible."
Senior Justice Department official Peter Kadzik sent assurances in a letter Monday to several leading Senate Democrats, who are angry that the FBI announced the renewed probe so close to the presidential election.
"We assure you that the department will continue to work closely with the FBI and together dedicate all necessary resources and take appropriate steps as expeditiously as possible," Kadzik wrote. "We hope this information is helpful."
FBI Director James Comey informed Congress on Friday that law enforcement officials will examine a new batch of Clinton emails found on a computer during the probe into former Congressman Anthony Weiner. He is the estranged husband of close Clinton aide Huma Abedin.
Weiner is accused of exchanging sexually explicit emails with a 15-year-old girl. Weiner and Abedin may have shared the same computer.
Comey said investigators found emails that may be germane to their earlier probe into emails sent and received by Hillary Clinton when she was secretary of state.
Clinton and Democrats were delighted when Comey suspended his investigation in July, saying that while Clinton was "sloppy" with the way she handled her emails, she did nothing criminal.
Comey has so far given no information about what investigators found to spark the new probe, and its timing close to Election Day has left Democrats and many Republicans scratching their heads and wondering what is going on.
WATCH: Clinton talks about the FBI's timing
"There's no case here," Clinton shouted at a campaign stop Monday in Ohio. She accused the FBI of getting involved in the election "with no evidence of any wrongdoing." She challenged investigators to look at the Abedin emails "by all means."
"I think most people decided a long time ago what they think about all of this," she said.
Republican presidential candidate Donald Trump, not surprisingly, welcomed Comey's decision, telling a rally in Michigan that "it took a lot of guts."
"What he did was the right thing," Trump said as he again accused Clinton of corruption. Trump campaign officials say if Comey decided to take another look at Clinton's emails at this time, then something is going on.
WATCH: Trump says Comey did "the right thing"
While the race for the White House has gotten tighter since the email controversy resurfaced, polls give Clinton as much as a 3-point lead over Trump nationwide.
Meanwhile, Democratic Party officials in four states — Arizona, Nevada, Ohio and Pennsylvania — are suing the Trump campaign for alleged voter intimidation.
The officials say Trump is breaking two longstanding federal laws intended to prevent voter intimidation.
They say Trump has used "noise and distractions" to try to keep likely Democratic voters away from the polls, especially in heavily African-American neighborhoods.
In the case of Pennsylvania, Trump has said law enforcement is needed in "certain areas" to make sure people do not vote five times. He also called for "poll watchers" to prevent cheating.
Many states allow poll watchers, but they must be highly trained and actually live in the areas where they are working.
Philadelphia journalist Solomon Jones writes: "By threatening to use police to monitor voters, Trump not only ignores the numerous studies proving that voter fraud is virtually nonexistent, he also resurrects the history that created the enmity between African-Americans and law enforcement."
The Trump campaign has yet to comment on the lawsuits.