House Republicans have widened their probe of Health and Human Services Secretary Kathleen Sebelius by asking the country’s largest health insurers for information on her fundraising for a nonprofit group promoting ObamaCare.

Leaders on the Energy and Commerce Committee said Friday they have written to 15 insurance companies and other groups asking whether Sebelius had contacted them to solicit funds for ObamaCare’s implementation.

Companies should hand over any internal communications that document conversations with Sebelius or discussions about her request, including emails, lawmakers wrote.

The Sebelius probe began when news broke that she was petitioning major healthcare players to contribute to Enroll America, a group tasked with educating the public about its new health coverage options under healthcare reform.