U.S. regulators probing potential fraud by China-based companiesincreased pressure on their auditors by formally accusingaffiliates of Big Four firms of withholding documents frominvestigators.

Deloitte Touche Tohmatsu CPA Ltd., Ernst & Young Hua MingLLP, KPMG Huazhen and PricewaterhouseCoopers Zhong Tian CPAsLimited have refused to cooperate with accounting fraudinvestigations into nine companies whose securities are publiclytraded in the U.S., the Securities and Exchange Commission said inan administrative order today. The order also named BDO China DahuaCo. Ltd.

China-based companies listed on U.S. exchanges have facedincreased scrutiny over the past two years after regulators becameconcerned that some firms may not be providing accurate financialstatements to investors. Investigators have struggled to obtaindocuments central to the probes because auditors, citing China'slaws, declined to cooperate.