BEIJING - Chinese police detained more than 4,500 suspects in the 1,900 cases of pyramid selling they investigated in 2011, according to figures released on Friday.

During the investigation, the police froze nearly 900 million yuan (143 U.S. dollars) of illegal assets, said a statement jointly issued by the Ministry of Public Security and the State Administration for Industry and Commerce.

Pyramid selling has been banned in China since 1998, but "remains rampant in some regions and is posing a growing threat to society," said the statement.

In response to the danger, the two agencies announced on Friday that police would crack down on such offenses under a new campaign which will run until the end of June.

The new campaign will focus on both traditional patterns of pyramid selling and Internet-based versions of the scam, said the statement.

It particularly noted the urgency of preventing pyramid selling in less developed western China and regions inhabited by ethnic minorities.