WASHINGTON — The Justice Department sent a brief letter to six lawmakers Monday, saying that it will work closely with the FBI to take "appropriate steps as expeditiously as possible" in the renewed investigation into emails potentially tied to Hillary Clinton's private email server.

The three-paragraph letter written by Assistant Attorney General for Legislative Affairs Peter Kadzik said that the department and FBI will "dedicate all necessary resources" to the investigation, but provided no further details about the contents of the emails or whether they are significant.

The short statement on behalf of Attorney General Loretta Lynch and FBI director James Comey represents an effort by the Justice Department to stabilize and assert control over a politically explosive situation set in motion Friday when Comey notified congressional leaders about the FBI's renewed inquiry.

Kadzik was responding to a letter sent Saturday to Lynch and Comey from Democratic Sens. Thomas Carper of Delaware, Patrick Leahy of Vermont, Dianne Feinstein of California and Benjamin Cardin of Maryland asking that law enforcement authorities provide by Monday more details of the investigative steps being taken by the FBI, the number of emails involved and what is being done to determine how many of the emails are the same as ones already reviewed by the FBI. The letter was also sent to Reps. Elijah Cummings, D-Md., and John Conyers, D-Mich.

On Friday, Comey set off a firestorm by telling the chairmen of eight congressional committees that the FBI would take "appropriate investigative steps" to determine whether newly discovered emails found in an unrelated investigation contain classified information and to assess whether they are relevant to the investigation involving Clinton's private email server. The unrelated case was an investigation of former Rep. Anthony Weiner, D-N.Y., the estranged husband of top Clinton aide Huma Abedin.

Justice officials have said that before Comey notified Congress, they warned him that doing so would go against long-standing practices of the department to not comment on ongoing investigations and to not take steps that could be viewed as influencing an election.

Officials familiar with Comey's decision said that he felt a sense of obligation to lawmakers to "supplement" his testimony under oath in July that the Clinton investigation was complete and there would be no charges. Comey was also concerned that word of the new email discovery would leak to the media and raise questions of a coverup, the officials said.

But his brief letter to lawmakers on Friday did not satisfy at least one of the recipients, Sen. Charles Grassley, R-Iowa, the chairman of the Senate Judiciary Committee.

Grassley wrote Comey on Monday saying that the disclosure he provided to Congress last week "did not go far enough" and was unfair to Congress and the American people.

"In the absence of additional, authoritative information from the FBI in the wake of your vague disclosure, Congress and the American people are left to sift through anonymous leaks from Justice Department officials to the press of varying levels of detail, reliability, and consistency," he wrote.

Grassley asked Comey to answer by Friday a series of questions about the email discovery.

White House spokesman Josh Earnest praised Comey as "a man of principle … integrity and talent," and said that President Barack Obama, who nominated Comey three years ago, does not think he is trying to influence the presidential election.