BEIJING - China's ChiNext Board, a Nasdaq-style index tailored for growth enterprises, tumbled Wednesday morning as the index began to erase gains prompted earlier in a profit frenzy.

During morning trading, the ChiNext Index sank more than 4 percent before trimming losses to close down 2.96 percent at 1,348.62 points.

Growth enterprises in the entertainment sector were hit the hardest. Beijing Enlight Media Co Ltd and Huayi Brothers Media Corporation both dropped to their daily limit of 10 percent in the morning.

China Business News (CBN) reported last week that speculative capital has flowed under the government's plan to restructure the economy and boost emerging sectors, including firms in electronics, entertainment, gaming and telecoms.

The index has risen more than 98 percent compared to the beginning of 2013, the report said.

Expectations for future growth of the index may be difficult to rationalize as speculation in the market has created a bubble, CBN said, citing research by China Southern Asset Management, a Shenzhen-based fund management company.

The finance channel on Chinese news portal Sina said that as of Tuesday, 57 percent of the 352 ChiNext-listed companies that had disclosed third-quarter reports had forecast net gains, compared to 56 percent for half-year reports.

The benchmark Shanghai Composite Index went down 1.35 percent to 2,203.34, while the Shenzhen Component Index lost 1.37 percent to finish at 8,581.44 by midday.