Private companies have expanded into capital-intensive industries that are often thought to be the domain of large corporations or State agencies, according to a national business survey.

From 2001 to 2005, investment and earnings of private companies in sectors such as steel, chemicals, coal, electricity and real estate saw large increases, the report said.

The metals smelting and processing industry has seen the fastest development for private companies, the report noted.

In 2005, sales revenue for private enterprises in the ferrous metals industry was 797.3 billion yuan, up from 88 billion yuan in 2000, an average annual growth rate of about 55 percent.

Apart from the metals sector, private companies also saw rapid expansion in the manufacturing and chemical industries.

Sany Corp, a private company in Central China's Hunan Province, has become one of the nation's leading makers of construction machinery.

The company now offers a range of construction equipment, including road building and hoist machinery. Its concrete pump is now the most popular product of its kind on the market, with about 40 percent of domestic sales.

The company said earlier it plans to build an assembly plant in the United States, becoming the first Chinese machinery company to open a factory in that country.

Sany will initially invest about $9 million in its US plant, with the amount rising to $50 million over three years, said Xiang Wenbo, Sany's executive president.

Privately owned petrochemical company Tongyi has grown rapidly in 13 years to become China's third-largest lubricants company. It has a network of 2,000 distributors and 90,000 retailers across the country and has three lube oil blending plants with a total annual capacity of 600,000 tons.