SHANGHAI -- A company traded on the Shanghai Stock Exchange for more than two decades was finally delisted on Wednesday after an investigation found it violated information disclosure rules.

Zhuhai Boyuan Investment Ltd. wrapped up its last day of trading at the Shanghai Stock Exchange at 4.49 yuan, up 2.75 from Tuesday, with transaction volume hitting 87.56 million yuan.

The company is the first to be delisted on the Chinese mainland for "major violations" as China's stock regulator improves delisting procedures to protect investors.

Analysts have long suggested that a sound delisting mechanism is crucial to turning approval-based IPOs into registration-based.

Previously delistings were mostly for failure to meet requirements on profitability. Some companies have managed to remain on the stock exchange through mergers and acquisitions by becoming a "shell" for other companies unwilling to go through the lengthy IPO pipeline.

Investors speculated on such shell companies when there was a lot of uncertainty around IPO reforms. Such speculation has been fueled since many U.S.-listed Chinese companies have offered to go private and plan a relisting at home. Shell companies could be a shortcut for them if they opt out of the usual IPO procedure.

Boyuan is just such a shell company. It traces its root back to Zhejiang Phoenix, one of the eight companies first publicly traded on the Shanghai Stock Exchange in the 1990s.

Over the years, it has been acquired, restructured and renamed, with its major shareholders shuffling through a revolving door, yet earnings have been disappointing.

In a market dominated by retail investors and driven by speculation, shares in Boyuan and many like it were chased for quick gains despite lackluster fundamentals. In June 2014, the China Securities Regulatory Commission began an investigation into Boyuan over information disclosure violations and in March 2015, the probe led to a police investigation.

The company was found to have repeatedly forged bank acceptance bills and other major transactions, and its financial statements included fraudulent information on assets, income, profit and other items.

Trading of Boyuan shares was suspended on May 14 last year after the company was flagged by regulator for delisting risk. When it resumed trading in March this year, its shares tumbled by the daily trading limit for four straight days.

Analysts say Boyuan's delisting could send a chill through the speculative fever around shell companies, long a target for investors looking for quick gains whenever there is rumor of a deal.