BEIJING, Feb. 1 -- Chinese manufacturing business activity continued to wane in January as a key index dropped to below 50 for the first time since October 2012, marking increasing downward pressures on the economy, official data showed on Sunday.

The manufacturing purchasing managers' index (PMI), a key measure of factory activity in China, posted at 49.8 in January, down 0.3 percentage point from December, according to the data released by the National Bureau of Statistics (NBS) and the China Federation of Logistics and Purchasing.

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

Zhao Qinghe, a senior statistician of the NBS, attributed the PMI retreat to the coming Spring Festival holiday and seasonal factors as manufacturing activity usually slows in the period.

Falling commodity prices and sluggish market demands also contributed to the drop, Zhao added.

In terms of the size of the surveyed enterprises, the PMI of large manufacturers posted 50.3, down from 51.4 in December but still marking expanding activity.

However, that of medium enterprises stood at 49.9, up 1.2 percentage points but still in a state of contraction. The PMI of small manufacturers recovered to 46.4, up from 45.5 in December, and remained in the contraction territory, the NBS said.