HONG KONG - PwC is making "tangible investments" to ensure the Big Four firm has high quality and sustainable business in China, it said in a memo to staff after Chinese regulators on Friday hit the company's mainland unit with a record penalty.

PwC Zhong Tian LLP was hit with a six-month suspension and a fine of 441 million yuan ($62 million) on Friday over the firm's audit of failed property developer China Evergrande Group .

Chinese authorities have been examining PwC's role in Evergrande's accounting practices since the country's securities regulator accused the developer in March of a $78 billion fraud over a period of two years through 2020.

"We want to recognize that this has been an extremely challenging period for all of you," said the PwC internal memo issued late on Friday after the regulatory penalty announcement, and reviewed by Reuters.

"The PwC network has also shown continued support for our China firm throughout this period... They are making tangible investments to ensure we have long term, high quality and sustainable business in China," it said.

PwC declined to comment.

"I know that the coming weeks will not be easy as we put in place a detailed remediation plan and begin to position the business for future success," the firm's new China territory head, Hemione Hudson, said in the memo.

PwC appointed its global risk and regulatory leader Hudson to replace China territory senior partner Daniel Li as part of its remedial actions. Li stepped down given his "former responsibilities" as head of the local auditing business.

The firm said that its leadership team would help staff "navigate any questions or concerns" they might have related to the Chinese regulatory announcements.

"One of my areas of focus will be on spending time with you and looking at ways of further developing our talent, including investing in you as our people," Hudson said in the memo.

The memo also said that PwC China had a long history of high-quality audits.

"We do not believe that the behavior of a very small number of engagement team members is representative of the work of the vast majority of PwC China's 18,000 professionals," it said.

Separately, regulators are continuing their investigation into PwC's work by its Hong Kong unit in relation to China Evergrande, which is a Hong Kong listed entity, according to mainland and Hong Kong regulatory statements on Friday.

The penalty announced by the mainland regulators "has laid an important landmark in cross-border law enforcement of China Evergrande", said a statement by Hong Kong's Accounting and Financial Reporting Council on Friday.

"Our independent investigation into China Evergrande will roll out in an orderly way," it said.

(Reporting by Xie Yu; Editing by Sumeet Chatterjee, Sonali Paul and Christopher Cushing)