The N.C. State Ethics Commission has launched an investigation into two lobbyists who had romantic relationships with top aides to House Speaker Thom Tillis, according to confidential documents obtained by The News & Observer.

The probe will examine whether lobbyists Jessica Hayes and Dean Plunkett violated the state's ban on gifts and failing to report expenses related to their relationships with legislative employees, according to letters the commission sent to the lobbyists in late May.

The commission is also investigating the N.C. Home Builders Association, which Hayes represented, and will contact Plunkett's numerous clients, which include the Association for Home and Hospice Care of North Carolina and the Coastal Conservation Association, the documents indicate.

The News & Observer reported in April that Hayes had an intimate relationship with Tillis' chief of staff Charles Thomas, who resigned upon questioning. Tillis later determined that his policy aide, Amy Hobbs, had an ongoing relationship with Plunkett and asked her to resign. Tillis later gave generous severance packages to Thomas and Hobbs.

Thomas and Hobbs are not identified as targets in the investigation because they no longer work for the state and no longer fall under the jurisdiction of the state ethics commission.

Democrats filed ethics complaints in May after reading the N&O report. Last week, the legislative ethics committee declined to investigate the matter, saying it doesn't have jurisdiction over the conduct of staffers and lobbyists. But the committee said it would draft rules to prohibit such conduct in the future.

The commission investigation is done behind closed doors. The lobbyists and home builders association have until later this month to file a response to the allegations.