HONG KONG (Reuters) - 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 record fine of 441 million yuan ($62 million) on Friday over the firm's audit of failed property developer China Evergrande Group ( EGRNF ).

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 did not immediately reply to Reuters' query on Monday.

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