Last year, KPMG LLP has avoided an indictment over its sale of questionable tax shelters by reaching a deferred-prosecution agreement with federal prosecutors. Now the government has widened its investigation into abusive shelters to include law firms, banks, and investment firms that helped accounting firms devise and promote them, according to The New York Times.

The Times reported last month that three lawyers at a prominent Dallas law firm, Jenkens & Gilchrist, are being investigated. The newspaper has also reported that federal prosecutors have contacted the law firm of Sidley Austin Brown & Wood; individuals at several banks, including Deutsche Bank; and several accounting firms, including Ernst & Young.

The paper stressed that it is unclear what transactions the government is looking into. None of the parties in question offered comment.

According to the Times, the three Jenkens & Gilchrist lawyers have been accused in a civil suit of writing hundreds of legal opinion letters in recent years approving tax shelters sold by accounting firms and by their law firm that did not meet Internal Revenue Service standards.

A lawsuit filed by an Indiana investor reportedly stated that one of the lawyers, Paul M. Daugerdas, used Deutsche Bank for transactions underlying a shelter called Cobra for scores of clients and participated in a conference call with Ernst & Young employees and others about the fees and workings of the shelter.