Las Vegas Sands faces US probes into Macau payments
Las Vegas Sands, one of Asia's biggest casino operators, is being investigated by regulators after an ex-employee accused it of making improper payments.
The company said it was being probed by the Securities and Exchange Commission, and the US Department of Justice.
Former Sands China chief executive Steve Jacobs accused the firm of using improper leverage against government officials.
The company is controlled by billionaire Sheldon Adelson.
Mr Jacobs made his allegations in a lawsuit he has filed against Las Vegas Sands. Mr Jacobs, who was fired by the company, is claiming breach of contract.
Las Vegas Sands said it will co-operate with the probe, and denied the allegations.
Las Vegas Sands said that the US watchdog and Department of Justice were looking into its compliance with the Foreign Corrupt Practices Act.
The act makes it illegal for companies to give foreign officials improper payments.
The company said that the Securities and Exchange Commission had asked it to produce documents related to its Macau operations.
The Department of Justice was carrying out a separate probe, the company disclosed in its annual report.
Carlo Santarelli, an analyst at Wells Fargo, said that "the headline risk will serve as an overhang on shares in the near term, until more on the matter is known".
Shares in the company, which operates three casinos in Macau, dropped more than 6% on the news in US trading.
Las Vegas Sands' growth is being driven by the success of its operations in Macau.
The Chinese territory has become the world's largest gambling market.
On Tuesday, the company reported that net profit at Sands China Ltd, more than tripled in 2010 to $666.5 million.
However, it warned that the ongoing investigation could have a further impact.
"Any violation of the Foreign Corrupt Practices Act or applicable anti-money laundering regulation could have a negative impact on us," it said.