It added the probe probably 'emanated from allegations contained in the lawsuit' from Jacobs, who was removed from his role running Sands China last July and is suing for breach of contract and US$10 million in severance pay and stock options.

In his suit, filed in a Nevada court last October, Jacobs accused Las Vegas Sands' billionaire founder Sheldon Adelson of directing him to 'threaten to withhold [Sands China] business from prominent Chinese banks' unless they used their influence on government officials to help Sands China with a property deal and labour quotas.

Macau has been extremely lucrative for Las Vegas Sands. Casinos in the former Portuguese territory raked in HK$19.2 billion in February - almost half the gambling dollars Las Vegas Strip casinos collected in the whole of last year.

On Monday, Sands China, which was spun off from its American parent in a Hong Kong iniial public offering in November 2009, reported net income for last year had risen 210 per cent to US$666.5 million.

But Jacob's lawsuit highlights the risks for foreign companies doing business in Macau, where political and business interests often overlap and where it can be difficult to escape brushing up against figures from the territory's triad-dominated past.

Jacobs also alleged Sands China risked breaching the Foreign Corrupt Practices Act by employing Macau lawyer Leonel Alves, a member of the territory's executive council.

The FCPA states American companies must not make payments to members of foreign governments.

The former Sands chief executive also claimed Adelson made him prepare a series of reports on prominent figures, including Cheung Chi Tai, a major investor in the listed gaming junket operator Neptune Group. He was named by Hong Kong prosecutors in an October 2009 trial as a leader of Macau's Wo Hop To triad.

Last month, Sands China filed a motion to dismiss the lawsuit, claiming Nevada was not an appropriate jurisdiction.

Aaron Fischer, an analyst with Asian investment specialists CLSA, said the US government could only take action against Las Vegas Sands, and that China Sands' licences might not be affected unless Macau regulators started their own investigation.

Sands shares closed yesterday at HK$17.86.

Under a cloud

Sands China annual profits rose: 209 per cent

The shares fell: 6 per cent

The casino operator is being investigated by the US Securities and Exchange Commission and Department of Justice.

Former chief executive Steve Jacobs accuses Sands China of:

- using 'improper leverage' with Macau government officials and Chinese banks

- Improperly employing a Macau government official

- preparing an investigative report on Cheung Chi Tai, an alleged triad leader