U.S. securities regulators have imposed sanctions against four Chinese accounting firms, which had refused to prove documents to investigators.

The U.S. Securities and Exchange Commission (SEC) said Friday it has settled with, and imposed sanctions against, four China-based accounting firms that belong to large international networks associated with the Big Four global accounting firms.

As part of the settlement, the commission censured the firms, which eventually began providing the documents, and requires them to perform specific steps to satisfy SEC requests for similar materials over the next four years. The firms also each agreed to pay US$500,000 and to admit that they did not produce documents before the proceedings were instituted against them in 2012. They agreed to the settlement without admitting or denying other findings in the order.

Under the settlement, if future document productions fail to meet specified criteria, the commission retains authority to impose a variety of additional remedial measures on the firms. An enforcement proceeding is also continuing against a fifth China-based accounting firm.

“As we repeatedly have stated throughout this litigation, obtaining an audit firm’s workpapers is critical to enforcement staff’s ability adequately to protect investors from the dangers of accounting fraud,” said Andrew Ceresney, director of the SEC’s enforcement division.

“This settlement recognizes the SEC’s substantial recent progress in obtaining those documents from registered firms in China,” he adds. “The settlement also holds four of the firms accountable for previously violating U.S. rules, and makes clear that should production of documents cease, the SEC can restart the administrative proceeding.”