Profits of China's major industrial firms maintained sound growth momentum in the first three quarters of the year as industrial production continued to recover and business operations kept improving, official data showed on Wednesday.

Industrial firms with annual business revenues of at least 20 million yuan (about 3.1 million U.S. dollars) saw their combined profits jumping 44.7 percent year on year in the January-September period to top 6.34 trillion yuan, data from the National Bureau of Statistics (NBS) showed.

The volume surged 41.2 percent compared with the 2019 level, putting the average January-September growth for 2020 and 2021 at 18.8 percent.

In September alone, profits of major industrial companies soared 16.3 percent year on year to 738.74 billion yuan, quickening from the 10.1-percent gain reported in August, according to the NBS.

In the first nine months, 29 out of 41 industries saw an expansion in their profits compared with the same period in 2019, while the overall performance of most industries was better than the pre-epidemic level, said senior NBS statistician Zhu Hong.

The high-tech manufacturing sector led the growth, with its profits growing 33.6 percent year on year over the same period.

In particular, boosted by the surging demand for vaccines at home and abroad, the pharmaceutical manufacturing sector continued high-speed growth since the beginning of the year and soared 66.8 percent during the period.

An obvious profit expansion in mining and raw material manufacturing industries has underpinned the headline figures, Zhu noted.

Profits in the coal mining industry jumped 272 percent year on year for the January-September period, while the oil and gas exploitation industry saw its earnings skyrocket 297 percent.

Zhu said that high commodity prices and unsmooth operations of supply chains have constrained the continuous improvement of the companies' profitability.

"The imbalanced profit distribution between upstream and downstream industries is meanwhile fairly prominent, and the foundation for the recovery still needs firming up," Zhu added.