The Caixin flash China general manufacturing PMI plunged to 78-month low at 47.0 in September from 47.3 in August, a preliminary Caixin survey showed on Wednesday.

    A reading above 50 indicates expansion, while a reading below that represents contraction.

    The sub-index on manufacturing output retreated to a 78-month low of 45.7 in September from 46.4 in August, according to the survey from Caixin Media Co., Ltd.

    "The decline indicates the nation's manufacturing industry has reached a crucial stage in the structural transformation process. Overall, the fundamentals are good," said Dr. He Fan, chief economist at Caixin Insight Group.

    He pointed out that weakening factory activity is tied to previous changes in factors related to external demand and prices.

    The flash index is published on a monthly basis ahead of final PMI data, making it the earliest available indicator of manufacturing conditions in China.

    The estimate is based on approximately 85 to 90 percent of total PMI survey responses from over 420 manufacturing companies each month and is designed to provide an indication of the final PMI.

    The final PMI for September will be released on Oct. 1.