HONG KONG (BLOOMBERG) - Jimmy Lai's Next Digital swung wildly in Hong Kong trading on Thursday (Sept 10) after local media reported police arrested 15 people in connection to last month's stock surge.

The arrests were made on suspicion of conspiracy to defraud and money laundering, Hong Kong news outlets including Cable TV and HK01 reported.

Police are expected to brief the media on Thursday afternoon, according to the South China Morning Post, which first reported the news.

After initially falling, shares of Next Digital soared as much as 97 per cent, mirroring last month's sudden gains.

"It's quite bizarre that local police rather than the markets regulator is investigating a stock market incident," said Mr Alvin Cheung, associate director with Prudential Brokerage in Hong Kong. "People might wonder if there's something else going on."

The extreme moves marked the latest twist in a drama that has captivated the financial hub since Lai was arrested last month under Hong Kong's controversial National Security Law.

Next Digital soared more than 1,000 per cent in a span of two days in August amid online calls to buy the stock in a show of support for Lai, one of Hong Kong's most prominent government critics.

Shares have since wiped out most of those gains after Hong Kong's securities regulator advised traders to exercise "extreme caution" and after Lai himself urged his supporters to avoid buying.

The rally in August followed a campaign by pro-democracy supporters to buy up the company's shares as a way to push back against his arrest.

Some Hongkongers and businesses that support the democracy cause have also been buying up advertisements in Lai's Apple Daily to show their support.

"People with very little money just want to express their anger and express their support for our company," Lai said in an interview with Bloomberg Television last month.

"Everybody bought a little bit. That became a lot of it and jacked up the price. I was telling people 'don't do it, don't do it, because you're going to lose money'."

Hong Kong's Securities and Futures Commission has requested brokers to submit client information and recent transaction records related to Next Digital's shares, the Hong Kong Economic Journal reported at the time, citing unidentified brokers.

More than 450 million Next Digital shares changed hands on Thursday, compared with a record 4.1 billion on Aug 11.