China's machinery industry has sustained mild recovery since last year but some key indices are showing signs of retreat, moderating any optimism, an official said on Thursday.

In the first four months, the value-added output of the machinery sector grew 11.5 percent year on year, outperforming the 8.7 percent rise in the broader industry, according to Cai Weici, vice president of China Machinery Industry Federation.

Some key indexes, such as investments and new orders are slowing. Fixed asset investments during January-April rose 14.1 percent year on year, down 2.42 percentage points from the rate during the same period last year.

"This shows business expectations are not high," Cai pointed out.

After a decade of development from 2001, machinery enterprises began to suffer from oversupply and homogeneous products that led to bankruptcies in 2011 before gradually gaining strength last year.

While cautioning enterprises to seek diversified or unique products, Cai predicted profit growth of 12 percent for the industry in 2014, with exports expected to increase 8 percent.