AUGUSTA — The Maine Turnpike Authority is reducing the number of credit cards issued to its staff, from 51 to 15, as part of an effort to improve financial oversight.

The authority has no evidence that employees have abused credit cards, said its spokesman Scott Tompkins, though lawmakers have raised concerns about the credit card expenses of former Executive Director Paul Violette.

From 2004 to 2009, Violette used his card to bill the authority $286,000 for hotels, meals and other expenses, according to credit card statements obtained by the Legislature’s Government Oversight Committee.

The committee has subpoenaed Violette to appear at a hearing April 15 and answer questions about the authority’s spending practices during his 23-year tenure. Violette resigned last month.

Violette’s credit card statements surfaced after the Legislature’s Office of Program Evaluation and Governmental Accountability spent several months reviewing the turnpike authority’s operations.

Peter Mills, a former Republican legislator, is now the authority’s interim director. In addition, the authority’s board of directors has hired Roger Mallar as a consultant. Mallar was Maine’s transportation commissioner under Govs. Kenneth Curtis, James Longley and Joseph Brennan.

Mills said the turnpike authority is in a strong financial position. He said it is one of three toll authorities in the United States with AA bond ratings, which means it can borrow money cheaply, saving millions of dollars.

He said he and Mallar are working to establish financial controls that will allow the authority to regain public trust.

Tompkins said 22 employees of the turnpike authority held a total of 51 cards. Some of those cards had expired, and some employees held more than one because vendors requested specific cards.

He said the returned cards have been cut up, and the accounts have been discontinued.

He said the remaining 15 cards are in the hands of nine staff members, who need them to buy goods and services for the authority’s day-to-day operations.

Tompkins said the use of those cards is subject to documentation requirements and review.

The board of directors also has decided to expand the scope of an accounting position to include an internal audit component.

The internal auditor will report quarterly to the board regarding the staff’s compliance with travel, meal and general spending policies, Tompkins said.