Two Tennessee Democrats on Wednesday called for the U.S. Attorney to investigate whether members of House Speaker Glen Casada's office secretly listened to lawmakers' private conversations in legislative committee rooms.

The calls from House Minority caucus chairman Mike Stewart and Rep. Bo Mitchell came after the USA TODAY Network - Tennessee reported the speaker's former chief of staff admitted to being able to eavesdrop on committee rooms, white noise machines were installed inside and outside Casada's office and several members raised concerns about their offices containing recording devices.

"I'm calling on the United States Attorney's office to immediately commence an investigation to determine whether or not the surveillance of private meetings with no consent violated state and or federal laws," said Stewart, D-Nashville.

Stewart sent a letter to the U.S. Attorney's office later Wednesday formally requesting a probe.

"It is suspected that the purpose of this system was to spy on meetings for which there was an expectation of privacy for all parties in attendance," he wrote.

Alex Little, a Nashville criminal defense lawyer and former assistant U.S. Attorney under Presidents George W. Bush and Barack Obama, said the accusations described in the USA TODAY NETWORK - Tennessee story, if true, appear to amount to a federal wiretapping offense.

"The allegation, as it's reported, would constitute a federal crime and certainly, given the circumstances involving a political opponent spying on somebody or the other party, is the sort of thing that's worthy of attention by law enforcement," Little said.

The federal prohibition on wiretapping also permits civil action in the form of a lawsuit, which Little suggested the Democrats could theoretically file against Cothren.

Jerry Martin, appointed by Obama to serve as U.S. Attorney for the Middle District of Tennessee from 2010 to 2013, said he believed it could be warranted for the FBI to at ask some questions about the allegations, but wasn't convinced that the livestream feed of committee rooms constituted a wiretapping violation.

"I have not heard anybody say they have located a device that was hidden in their office," Martin said. "Short of that, I don't know where it goes, but I think you have to take it seriously if you have a group of elected officials asking you to look into something."

In a statement, Casada later dismissed the notion that his office would "bug someone else's office" calling it "laughable and patently false." The speaker did not address the issue regarding the audio-video system of the House committees.

Stewart said the latest revelations about the House activities is akin to behavior in weak and developing countries.

"This is a grave and serious matter," he said, calling for a review of the technology and personnel involved.

Mitchell, D-Nashville, reiterated Stewart's call, saying such a probe needs to start quickly due to the fear of possible evidence being destroyed.

Mitchell also questioned whether the phones in lawmakers' offices are being used as an intercom system to hear what is being said.

The two Democrats were not the only lawmakers on Wednesday to raise the issue of potential surveillance at the legislature. During a midday conference call with members of the House Republican caucus, Rep. Bill Dunn, R-Knoxville, briefly touched on the issue.

"When we hear that people might be bugging offices, it's not like that's a wild notion. It's people saying, well I better sweep my office because there seems to be some kind of truth to it." said Dunn.

During the conference Dunn called for Casada to resign as speaker. Dunn would immediately become speaker if Casada were to step down.

Tennessee lawmakers typically use their legislative offices as safe havens where they can privately discuss policy and politics and meeting with constituents.

But this year, several lawmakers expressed fear that someone might be recording what they say in those private meetings.

Several lawmakers told the USA TODAY Network - Tennessee that they had or wanted to have their legislative offices swept for recording devices.

Allegations come amid scandal involving Casada-Cothren text messages

The latest reports come amidst the fallout of a separate USA TODAY Network - Tennessee report that found Cade Cothren, Casada's now former chief of staff, had a history of sending sexually explicit text messages and making inappropriate advances toward former interns, lobbyists and campaign staffers.

In some instances, Cothren included Casada, R-Franklin, in messages containing derogatory comments toward women.

On Wednesday, Gov. Bill Lee, for the second day in a row, fielded questions about whether he believed Casada should remain as speaker.

The governor also said it was premature to decide whether to call a special session or if the state authorities should investigate the matter.

"I think what’s unfolded in the last couple days is disturbing," said Lee. "And the people of Tennessee deserve to have an environment on Capitol Hill that’s respectful, that holds to a high standard we all expect."

Revelations about Cothren’s inappropriate sexual advances and text messages come after Casada’s chief of staff admitted to using cocaine in the legislature’s office building. Cothren is also facing scrutiny over racist text messages.