Landing did not provide any details on the investigation, but added it had been unable to contact Yang since Aug. 23.

Shares of the company jumped as much as 45 percent to HK$3.97 Tuesday, the highest since Aug. 23.

Landing shares had plunged more than 30 percent after the company reported on Aug. 24 that it had been unable to contact Yang for over a day. The news had come only weeks after the firm's $1.5 billion casino project in the Philippines was halted by authorities.

"Mr. Yang explained that he has been assisting the relevant department of the People's Republic of China with its investigation during the period of his absence," Landing said in a filing to the Hong Kong bourse.

The company's business and operations have been steady and normal during the period while Yang was absent, it added.

Yang was involved in property development in China's eastern Anhui province before joining Landing in 2013. Casino executives said he has a close relationship with Macau junket operators, who facilitate the VIP high-roller gambling business.

(Reporting by Donny Kwok; Editing by Anne Marie Roantree and Himani Sarkar)