Image copyright AP Image caption Mr Yim had been uncontactable since 18 November

Hong Kong listed brokerage firm Guotai Junan International says its chairman Yim Fung is back at work, after being missing for more than a month.

The firm said in a statement that Mr Yim had returned after "assisting in certain investigations" in mainland China.

Neither Mr Yim nor the company were the subject of the investigation, it added.

Several high profile Chinese executives have gone missing or been detained in the past few months.

Guotai Junan International's parent company, Guo Tai Junan Securities, is one of the biggest in mainland China.

The mystery behind China's 'missing' bosses

Mr Yim went missing on 18 November. Guotai Junan International's shares fell as much as 17% when it first announced that it could not contact Mr Yim, and had to appoint a temporary replacement.

In a statement, Guo Tai Junan International said it was informed of Mr Yim's whereabouts on Tuesday, and that he "had been assisting in certain investigations carried out by Mainland authorities during the period he was unable to be reached".

It said Mr Yim would resume his duties as chairman, executive director and chief executive officer as of Wednesday.

"The board confirms that the current operations of the company are normal and stable," it added.

In a similar case earlier this month, high-profile Chinese tycoon Guo Guangchang went missing for several days.

His company also later revealed The Fosun International chairman had been assisting authorities with a probe.

Mr Guo said he could not give more details as the investigation was "sensitive".

The Chinese authorities have launched a campaign against corruption in the financial sector, following a severe slump in China's stock market over the summer.