Nearly two months after the House ethics committee acknowledged it is investigating lawmakers’ ties to the PMA Group — a statement made in the wake of demands for public accountability — little is known about the inquiry because the panel is using a process that limits the amount of information it has to release.

Although the Committee on Standards of Official Conduct, commonly known as the ethics committee, announced in mid-June that its leaders had approved a “review of certain, specific allegations,— it has not named lawmakers or even which House rules it is examining.

“The Committee is currently reviewing certain allegations involving the PMA Group and its alleged conduct with respect to matters within the Committee’s jurisdiction,— ethics Chairwoman Zoe Lofgren (D-Calif.) and ranking member Jo Bonner (R-Ala.) said in their second statement on the matter, issued Thursday.

According to its earlier statement, the panel is reviewing the PMA Group under an internal regulation formally referred to as “Rule 18(a)— governing a “committee-initiated inquiry or investigation.—

Unlike some methods the ethics panel may use to initiate an investigation, such as the receipt of a formal complaint from a Member, inquiries under Rule 18(a) do not trigger any mandatory deadlines for votes or other actions.

In addition, when the committee opts to establish an investigative subcommittee to review a suspected rules violation, there is a precedent for disclosing such an inquiry to the public. The committee’s PMA investigation faces no such precedent.

Although the ethics panel acknowledged its review of PMA, the committee did so only after the House approved a resolution requiring disclosure of whether an investigation of the now-defunct lobbying group was under way.

Individuals knowledgeable of the House ethics process describe Rule 18(a) reviews as the most common investigations conducted by the committee. In the 110th Congress, the ethics committee conducted 14 investigations of Members and three of House employees under the rule, according to the committee’s biennial report. Seven of those investigations were concluded with no formal action by the panel.

The popularity of 18(a) investigations stems in part from the ease of instigating such a review, which under committee rules requires only the approval of the panel’s chairwoman and ranking member.

Those reviews also permit committee staff to conduct any necessary interviews and collect documents on a voluntary basis, and they can ultimately lead to more formal investigations. However, there are some limitations as well: Such investigations cannot issue subpoenas, which require the vote of either the full ethics panel or a subcommittee.

“It would be helpful if the ethics committee leaders would make clear to the public what areas or what ethics rules are involved in this investigation,— Democracy 21 President Fred Wertheimer said. “As of now, the public doesn’t have any information about what this investigation or inquiry is looking at and therefore has no way to know what the scope and parameters of the investigations— are.

Because the creation of an investigative subcommittee or the issuance of a subpoena are often the only indications of activity in the highly guarded ethics process, reviews under Rule 18(a) are less prone to publicity than more formal investigations.

It remains unclear what the ethics committee is focusing on in its PMA review.

The FBI raided the defense appropriations-focused shop in November, and the Justice Department appears to be focused on whether the firm used “straw man— contributions to funnel campaign cash to lawmakers.

It is not known whether the ethics panel is examining a small group of senior Democratic appropriators who received significant campaign contributions from PMA or the potentially larger pool of Members who designated earmarks for PMA clients or received campaign funds from those sources.

According to the Center for Responsive Politics, Appropriations Subcommittee on Defense Chairman John Murtha (D-Pa.) and panel members Peter Visclosky (D-Ind.) and Jim Moran (D-Va.) received about $4.8 million in campaign contributions over the past decade from PMA and its clients. The lawmakers helped those clients secure tens of millions of dollars in targeted projects during that period.

Murtha, Moran and Visclosky did not return telephone calls for comment Monday. Visclosky acknowledged in late May that federal investigators had issued subpoenas to his office and some employees as part of a grand jury probe of his ties to PMA.

Other lawmakers who have received notable contributions from PMA, including Reps. Patrick Murphy (D-Pa.) and Christopher Carney (D-Pa.), also did not return calls seeking comment.

Aides to Rep. Norm Dicks (Wash.), the third-ranking Democrat on the Appropriations panel, and Reps. Bill Pascrell (D-N.J.) and Tim Ryan (D-Ohio) said Monday that their offices had not been contacted to date by the ethics panel.

There are also no indications PMA has been contacted by the committee. An attorney representing PMA declined to comment for this article.

Individuals familiar with the ethics process note, however, that in typical inquiries, Members are not contacted until the final stages of an investigation.

Tory Newmyer contributed to this report.