Sen. Edward M. Kennedy of Massachusetts, chairman of the Senate’s education committee, said today that two major student-loan companies, Sallie Mae and Nelnet, may have broken federal law by using “harsh and inappropriate tactics” with borrowers whose payments were overdue.

In letters to the chief executives of both companies, Mr. Kennedy requested documents about students who took out loans under the guaranteed-loan program and whose loans have since become delinquent or entered collection. The inquiry represents the first time Mr. Kennedy, who has pursued an investigation into the student-loan industry, has looked into lenders’ practices with delinquent borrowers.

Sallie Mae, Mr. Kennedy charged, may have threatened a borrower with jail if the borrower failed to pay; may have used abusive language and harassed borrowers’ families and friends; and may have fired employees who tried to help students obtain information about their loans. Mr. Kennedy also alleged that the company may have intentionally sent borrowers’ bills to the wrong addresses in order to force the account into default.

Tom Joyce, a spokesman for Sallie Mae, said the company would cooperate with the request for documents. But he said in an e-mail message that the company had helped push default rates to record lows, and he criticized Mr. Kennedy for sending his letter to the news media before he sent it to Sallie Mae.

“It raises the question as to whether the facts are important in this inquiry,” Mr. Joyce said, “and whether the matter has been prejudged.”

Senator Kennedy alleged that Nelnet may have engaged in a much shorter list of harsh practices, including refusing to provide loan information to students and consolidating loans without a borrower’s consent. Nelnet did not immediately respond to a request for comment. —Josh Keller