The biggest acquisitions have been made by state-owned companies, but the role of smaller, private companies is growing.

Liu and his ex-wife were detained in Beijing before they returned to his home province of Sichuan, the Shanghai Securities News said, citing unidentified sources. It said other relatives were detained in Sichuan.

Beijing police did not respond Thursday to questions by phone and fax about whether Liu was detained.

A search for Liu's name on China's most popular microblog service, Sina Weibo, returned the notice, "according to relevant laws and regulations, the results for 'Liu Han' are not displayed" â¿¿ a possible sign authorities were trying to suppress discussion of his disappearance.

Liu was No. 148 last year on Forbes magazine's list of the richest Chinese businesspeople, with a fortune estimated at $855 million.

Hanlong was founded in 1997 and has interests in mining, construction of hydroelectric power, highway and tourism infrastructure and other businesses with a total workforce of more than 12,000 people, according to its website.

Sichuan Jinlu Group, where Liu also is chairman, produces polyvinyl chloride and other chemicals.

In 2010, a Hanlong subsidiary said it planned to invest $5 billion in steel-related materials including molybdenum and manganese and renewable energy projects in Australia.

In an interview the same year with The Wall Street Journal, Liu said his car was once shot up by an investor who suffered losses due to his aggressive investment style.

"They call me, 'Liu Han, the only survivor,' " Liu was quoted saying.

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AP researcher Fu Ting in Shanghai contributed.

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