Updated

House Republicans are expanding their investigation into Health Secretary Kathleen Sebelius' campaign to solicit support for a pro-ObamaCare group, after she acknowledged reaching out to companies her agency regulates as part of that effort.

The Department of Health and Human Services has maintained all along that the solicitations were legal and above board. Sebelius said as much when she testified before a House committee on Tuesday.

But she piqued the curiosity of Republican lawmakers after she acknowledged reaching out to three major companies the agency regulates -- Johnson & Johnson, Kaiser Permanente and Ascension Health.

Lawmakers want to know if an ethical line was crossed.

Sebelius apparently did not ask for donations from those three groups, but House Energy and Commerce Committee leaders said Tuesday they were expanding their probe over these revelations. They sent letters to two of those companies asking for more details about the conversations -- the lawmakers have cited rules that bar officials from fundraising from groups their agencies might regulate.

"The recent revelations made by Secretary Sebelius raise significant red flags about how she and others at HHS have been working on behalf of Enroll America," Energy and Commerce Committee Chairman Fred Upton, R-Mich., and and Oversight and Investigations Subcommittee Chairman Tim Murphy, R-Pa., said in a statement.

The department has previously acknowledged that Sebelius asked H&R Block and the Robert Wood Johnson Foundation for donations to Enroll America -- HHS does not regulate those groups.

Republicans, while launching their own investigation, have separately called for independent investigations by both the inspector general for HHS and the Government Accountability Office.

Enroll America is a nonprofit organization helping to promote and implement the 2010 health care overhaul.