BEIJING - China's nonferrous metal sector saw a robust expansion in the first half of this year, with the profits of major nonferrous metal firms hitting a record high, industry data showed.

From January to June, major companies in the sector raked in 163.97 billion yuan ($25.37 billion) in profits, surging 224.6 percent year-on-year, according to the China Nonferrous Metals Industry Association.

The volume increased by 35.66 billion yuan from the 2017 level, with the four-year average growth rate for the Jan-June period standing at 6.3 percent.

The sector's debt-to-asset ratio fell during the same period. By the end of June, the debt-to-asset ratio of China's major nonferrous metal companies came in at 60.6 percent, down 2.8 percentage points from 2017.

The output of 10 types of non-ferrous metals including copper and aluminum reached 32.55 million tons in the first half, rising 11 percent year-on-year.

More money were pumped into the sector after years of investment decline, as the fixed-asset investment to the sector in the first half went up 15.7 percent from the same period a year ago, the association said.