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 January-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 nonferrous metals including copper and aluminum reached 32.55 million tons in the first half, rising 11 percent year-on-year.

More money was 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.