(Bloomberg News) U.S. regulators are accusing China-based affiliates of the Big Four accounting firms of refusing to produce documents related to investigations into financial disclosures at firms based in that country.

Deloitte Touche Tohmatsu CPA Ltd., Ernst & Young Hua Ming LLP, KPMG Huazhen, PricewaterhouseCoopers Zhong Tian CPAs Limited, and BDO China Dahua Co. Ltd. have refused to cooperate with accounting fraud investigations into nine companies whose securities are publicly traded in the U.S., the Securities and Exchange Commission said in an administrative order today.

China-based companies listed on U.S. exchanges have faced increased scrutiny over the past two years after regulators became concerned that some firms may not be providing accurate financial statements to investors. Investigators have struggled to obtain documents central to the probes because auditors, citing China’s laws, declined to cooperate.

“Only with access to work papers of foreign public accounting firms can the SEC test the quality of the underlying audits and protect investors from the dangers of accounting fraud,” SEC Enforcement Director Robert Khuzami said in a statement. “Firms that conduct audits knowing they cannot comply with laws requiring access to these work papers face serious sanctions.”

The SEC has de-registered the securities of nearly 50 companies and filed fraud cases against more than 40 issuers and executives as part of its investigation into the non-U.S. based issuers. Many of the companies entered U.S. capital markets through so-called reverse mergers, in which a closely held firm buys a shell company already listed on an exchange, allowing them to sell shares without the scrutiny that would surround a public offering.

Earlier this year, the agency announced a separate enforcement action against the Shanghai-based Deloitte affiliate after seeking to enforce a subpoena in federal court.

“Ernst & Young Hua Ming supports close working relationships between regulators to enable them to cooperate and share information with one another,” Will White, director of global and EMEIA media relations for Ernst & Young, said in an e-mail statement. “We hope that an agreement can be reached between U.S. and Chinese regulators that will enable our compliance with all applicable laws and regulations.”

Geoffrey F. Aronow, an attorney for KPMG at Bingham McCutchen LLP, declined to comment. An e-mail sent after working hours to KPMG China spokeswoman Nina Mehra wasn’t immediately returned. E-mails to attorneys for Deloitte and PricewaterhouseCoopers weren’t immediately returned.

The Ontario Securities Commission, Canada’s largest financial markets watchdog, earlier today released a statement of allegations against Ernst & Young LLP, claiming the firm didn’t conduct audits of now-insolvent Chinese tree-plantation operator Sino-Forest Corp. according to accounting industry standards.