Washington (CNN) A pair of House Democratic lawmakers is asking the National Rifle Association to answer questions related to potential ties to Russia, including on the gun rights organization's finances, a 2015 trip to Moscow attended by NRA backers and whether NRA officials communicated with Russian-linked individuals about attempts to interfere in the 2016 US presidential election.

The letter, dated Friday, is addressed to NRA CEO Wayne LaPierre and signed by Democratic Reps. Ted Lieu of California, a member of the House Judiciary Committee, and Kathleen Rice of New York, a member of the House Homeland Security Committee.

This isn't the first time the NRA has faced scrutiny from Democratic lawmakers.

Democratic Sen. Ron Wyden of Oregon has sent multiple requests to the organization asking about its finances. And earlier this month, Sen. Sheldon Whitehouse and Rep. Jamie Raskin, both Democrats, sent a letter to the NRA asking for information about donations the group funneled toward the Trump presidential campaign and GOP congressional candidates.

If House Democrats -- who now hold a majority in the lower chamber of Congress -- decide to make use of their subpoena power to target the NRA, that could create another headache for the gun rights group.

In response to a request for comment on the letter from Lieu and Rice, William A. Brewer III, who serves as counsel to the NRA, told CNN that the organization "has not yet received the letter," but intends to "respond to all appropriate information requests."

"Although the NRA has not yet received the letter, the Association, naturally, will respond to all appropriate information requests," said Brewer, partner at Brewer, Attorneys & Counselors and counsel to the NRA, in a statement. "The NRA is working diligently to supply information in response to several requests for information, and will continue to do so."

Lieu and Rice write in their letter that they have become "increasingly alarmed" by what they describe as "the complex web of relationships between individuals associated with the NRA and highly influential Russian officials" and say that it is "imperative that Congress has a full understanding" of efforts by Russia to influence US elections.

2015 Moscow trip

The letter asks several questions about a 2015 trip to Moscow attended by NRA backers.

The 2015 trip was orchestrated by former NRA president David Keene and Maria Butina, a Russian native who pleaded guilty in federal court in December to conspiring to act as a foreign agent. As part of her plea, she admitted to attempting to infiltrate Republican political circles and influence US relations with Russia before and after the 2016 presidential election.

The agenda included events with Alexander Torshin, a Russian government official who was later sanctioned by the US Treasury Department, as well as former Russian Deputy Prime Minister Dmitry Rogozin, who had already been sanctioned by the US government.

Butina worked closely with Keene and his wife to organize the 2015 Moscow trip. Keene used his NRA email address in making the arrangements as did another NRA staffer named Nicholas Perrine, according to emails obtained by CNN.

Among the attendees in 2015 were Keene, Dr. Arnold Goldschlager, an NRA donor; Joe Gregory, a prominent NRA fundraiser; Jim Liberatore, president and CEO of the Outdoor Channel; Sheriff David A. Clarke Jr., who was a prominent Trump surrogate during the campaign; and Pete Brownell, who would later serve as NRA president.

Goldschlager described the 2015 Moscow visit as a "people-to-people mission" in an interview with McClatchy last year and said, "The trip exceeded my expectations by logarithmic levels."

The letter asks, "What expenses did the NRA pay for the December 2015 trip to Moscow?" and "Did any NRA officials communicate with Torshin, Butina, or any other Russia-linked individuals about efforts to interfere in and influence the 2016 U.S. presidential election?"

It also asks, "Did the NRA facilitate any meetings or communications between Trump campaign associates and Torshin or any other Russia-linked individuals?"

The NRA has attempted to distance itself from the trip. In a statement to CNN earlier this month, Brewer said that LaPierre was "personally opposed" to the trip when he found out about the details of the visit.

"When he became aware of the details of the trip, Wayne was personally opposed to it," Brewer told CNN, adding, "In order that the group was not viewed as representing the NRA, Wayne spoke with several people about the excursion. As a result, Mr. Cors agreed not to make the trip. In addition, NRA staff members who were in Israel (for a trip that preceded the visit to Russia) returned home." Cors was NRA president at the time the trip took place.

But CNN has confirmed that NRA officials appeared to play a significant role in planning the trip.

At least one NRA employee assisted Butina in making travel arrangements for the delegation that would be visiting Moscow. At one point, the NRA employee even asked whether the NRA should be listed as the organization that was footing the bill for some of the NRA-affiliated attendees, according to emails obtained by CNN.

The letter references recent news stories on the origins of the 2015 trip, saying, "Recent reporting, however, suggests that the NRA was in fact involved. For example, the emails reviewed by reporters suggest that the NRA covered the travel expenses of some delegates and that NRA employees worked with Butina and other Russian individuals to make travel arrangements."

Lieu and Rice write, "We are disturbed by the lack of transparency the NRA has demonstrated surrounding the December 2015 trip to Moscow."

More questions about NRA finances and Russia

The letter asks questions related to the gun rights group's finances, including, "How much money did the NRA receive from Russia or Russia-linked individuals or entities during the 2016 election cycle?"

Lieu and Rice also ask, "Did the NRA use any of that money in their 2016 election campaign contributions?" and "Did any NRA officials discuss money laundering or the funneling of money from Russia to the NRA?"

After facing questions about whether foreign money could have been funneled through the group to boost the Trump campaign, the NRA has insisted that it did not use foreign funds for election-related purposes, but has acknowledged that it accepts money from foreign donors.

Wyden asked the NRA, which supported Trump during the 2016 election and spent millions of dollars to back his candidacy, in March if it can "categorically state" that "your organizations have never, wittingly or unwittingly, received any contributions from individuals or entities acting as conduits for foreign entities or interests?"

The NRA's secretary and general counsel John Frazer said in a mid-March response that the NRA takes pains to ensure money from foreign nationals isn't injected into political spending.

"While we do receive some contributions from foreign individuals and entities, those contributions are made directly to the NRA for lawful purposes," Frazer wrote. "Our review of our records has found no foreign donations in connection with a United States election, either directly or through a conduit."

While it's not illegal for the NRA to accept contributions from foreign donors, the group would run afoul of the law if that money were used for electioneering purposes. The NRA's political action committee, the NRA Political Victory Fund, is required to report its spending to the Federal Election Commission, but the group houses a number of other accounts that aren't bound by such transparency.